Unit+1+General+Physics+Mass+Weight+and+Forces

=// 1.3 Mass and weight //= LOs: • Show familiarity with the idea of the mass of a body • State that weight is a force • Distinguish between mass and weight • Recall and use the equation W = mg • Demonstrate understanding that weights (and hence masses) may be compared using a balance
 * Supplement **
 * • Demonstrate an understanding that mass is a property that ‘resists’ change in motion **
 * • Describe, and use the concept of, weight as the effect of a gravitational field on a mass **

//Questions to think://

> > > > > >
 * 1) True or False: Two objects with the same volume always have the same mass.
 * 1) What weighs more, a pound of lead or a pound of feathers?
 * 1) Which weighs more 100 pennies on the earth or 100 pennies on the moon?
 * 1) What is the meaning of “weightlessness” ?
 * 1) Can you be weightlessness?
 * 1) Can you be massless?
 * 1) You have just landed on Planet X. You take out a ball of mass, m, release it from rest from a height of h, and measure the time, t, that it takes to reach the ground. You can ignore any force on the ball from the atmosphere of the planet. How much does the ball weigh on the surface of Planet X? It depends on the mass of the planet, the radius of the planet, and the height you are holding it.
 * 2) You are in a lift and you are about to go upwards. If you are on a weighing scale in the lift and the lift just starts going up, what would happen to the reading of the weighing scale?

Find your answers while watching the video clip below. media type="youtube" key="OJIrAEvGkhk" width="560" height="315" [|Gravity S106LS29][|Lammas Science]  Published on 9 Dec 2012

**Homework:** **Define what mass and weight are. Describe the differences between them.** **Mass** (The amount of 'substance/matter' in an object) The __ resistance __ to move. Mass is a property that resists motion. The greater the mass of the same size and shape, the harder to change its motion. (INERTIA) Mass is independent of gravity. It is the same anywhere in the Universe. It is measured in __ kilograms __ [ kg ].
 * Mass from youtube Eureka episode || Mass & Weight from youtube Eureka episode ||
 * media type="file" key="Mass.flv" width="344" height="258" || media type="file" key="Weight vs Mass.flv" width="344" height="258" ||

=Weight= The effect of gravity on a mass. It is the __**force**__ of gravity on an object and is measured in __Newtons__ [N]. Weight is a vector quantity. Its force depends upon 2 things. Weight is caused by the gravitational field of Earth on a mass.
 * gravitational acceleration
 * mass

W = F = mg
 * m is mass (kg)
 * g is acceleration due to gravity (metre/second/second)

ie) Lorries are harder to jump start than cars. Weight is a force -> Weights are found using a scale. We can compare weights using a scale and thus, we can compare masses. To find mass, we use a measuring balance (Task: Find an image of a double beam balance). media type="youtube" key="1whMAIGNq7E" width="307" height="232" [|The Mass vs Weight song] by Mr. Edmonds YouTube [|Mass & Weight calculation] from www.gcse.com

[|Force Gravity and Weight from BBC GCSE BITESIZE] [|Gravity and Weight from Newton's homepage] [|Planet from BBC BITESIZE]

WEIGHT - The force of gravity on a body. W = mg, where W is weight/ N; m is mass/ kg; g is gravitational field strength/ Nkg -1. On Earth, g = 9.81 Nkg -1 =// 1.5 Forces //= FRICTION: The force which opposes motion when one surface moves over another. It is caused by the roughness of the surfaces. It is the force between two surfaces which impedes motion and results in heating NORMAL/REACTION FORCE: Two objects in contact each exert a force on the other which is perpendicular to the surface. TENSION: A force produced in a body when opposing forces are stretching it. The opposite is a compression force when two forces are squashing a body. UPTHRUST: An upward force on a body which is immersed in a fluid (liquid or gas). LIFT: An upward force on the wing of an aircraft due to the air flowing around it. INERTIA: The property of matter which makes it resist acceleration.

media type="youtube" key="MEXKwK6NGSM" width="560" height="315" [|If a Weight Drops In a Closed Container Does the Total Weight Decrease?] [|The Action Lab] Published on 14 Dec 2017
 * EXPLORATION QUESTION 1: Does the total weight decrease, if weight drops in a closed container? **

__Newton's 1st law (Inertia)__
Everything at rest will stay at rest unless there is a force applied to it. Everything in motion will stay in motion unless there is a force applied to it.

Force = mass x acceleration
The bigger the force acting on the object, the bigger the acceleration it gives to the object. Figure 3.10 on your text page 31. The increasing speed of a falling ball image shows the acceleration due to the gravity acting on it.
 * Quantity ||= Symbol || SI unit ||
 * force ||= **F** || The unit of weight (force) is the Newton, N ||
 * mass ||= **m** || The unit of mass is the kilogram, kg ||
 * acceleration ||= **a** || The unit of acceleration is the metres per second squared, m/s 2 ||

Question A A car of mass 1000Kg moving at 15 m/s hits a barrier and stops in a time of 0.1 s.

(a). Calculate its deceleration.

(b). What force would the car experience?

Question B A hovercraft moves on a cushion of air which is trapped underneath it. The trapped air reduces friction.

(a) The hovercraft starts from rest and as it starts the propeller produces a forward force F of 22,000 N. The mass of the hovercraft is 25,000 kg. Calculate the initial acceleration of the hovercraft. You may assume there is no friction.

(b) Some time later, the hovercraft reaches a steady speed, even though the force F is unchanged. Suggest, in terms of the forces acting on the hovercraft, why the speed is now constant?

Click the link and solve the Quizz on Force, Gravity, Mass, Weight.

__Newton's 3rd law__
For every action, there is an equal and __o pposite __ reaction.

1.5.1 Effects of forces LOs • Describe the ways in which a force may change the motion of a body • Find the resultant of two or more forces acting along the same line • Recognise that if there is no resultant force on a body it either remains at rest or continues at constant speed in a straight line • Understand friction as the force between two surfaces which impedes motion and results in heating • Recognise air resistance as a form of friction media type="youtube" key="eGZNocni6zE" width="448" height="251"

A force is a p__ ush __ or p__ ull __ in a particular direction. A force causes a__ cceleration __ since it changes in the s__ peed __ or direction of an object. A force is measured in __ Newtons[ __[__ N __]. Forces usually cannot be seen but their effects can. Forces usually acts in pairs. Forces can push or pull in any direction and more than one force can act on an object at a time. Ex) A force of 10N is roughly the amount of force the Earth's gravity pulls on a 1 kg mass.

EXERCISE: Fill in the blanks below 1. A force can cause a stationary object to start__ moving __. 2. A force can cause a moving object to increase s__ peed __. 3. A force can cause a moving object to d__ ecrease __ speed. 4. A force can cause a moving object to __ change __ its __ direction __ of motion. 5. A force can represented by arrows. A **force can ** cause an object to move or speed up (accelerate), to slow down (decelerate), to stop, or to **change ** direction. Any **change ** in velocity is considered __ acceleration __ and thus, a **force ** on an object results in the acceleration of an object.

**Resultant force:**
The resultant force is the single force that has the same effect as two or more forces acting on it. The combination of all the forces acting on an object is the net/resultant force.

The net force is equal to the __sum__ of the two forces when two forces act in the __same__ direction on an object. The net force is equal to the __difference__ of the two forces when two forces act in __ opposite __ directions on an object.

**Balanced forces;**
If two forces of equal strength act on an object in opposite direction, resulting in a net force of zero and no change of motion, forces are balanced. Two or more opposite forces acting on an object and if their effects cancel each other and they do not cause a change in an object's motion is known as balanced forces.

If the effects of the forces don't cancel each other, if one force is stronger than others, the forces are un__ balanced __. Unbalanced forces cause a c__ hange __ in motion; speed or direction or both

For an object with zero acceleration, the different forces acting on it are__ balanced __ or add up to zero; the resultant(or net force) is zero. __Fig 3.6 b on your text page 29.__

**Falling through the air**
Describe a speed against time graph for a falling parachutist. Explain what the terminal velocity is. Skydiving __**Task: Plot a speed against time graph of**__ __**a falling parachutist in the animation.**__ ( __**Graph**__ of terminal velocity during a parachute jump from absorblearning.com)

**Terminal velocity**
As a skydiver jumps out of a plane she accelerates because gravity pulls her down. The air resistance increases as her speed increases and so she starts to slow down. She reaches a terminal velocity - but at this speed she would most probably splat when she hits the ground. By using a parachute, she increases her air resistance and so lower her terminal velocity so that it is safer to land.

Notice that a parachutist's weight is constant. When air resistance equals weight, the forces are balanced and the parachutist reaches a steady speed. This is called as the terminal velocity. The acceleration is upwards when she opens her parachute, then she reaches at the new terminal velocity.

__Fig 3.13 and 3.14 on your text page 33.__

1.5.5 Scalars and vectors
 * Supplement **
 * • Understand that vectors have a magnitude and direction **
 * • Demonstrate an understanding of the difference between scalars and vectors and give common examples **
 * • Add vectors by graphical representation to determine a resultant **
 * • Determine graphically the resultant of two vectors **
 * Scalars: Magnitude (or numerical value) ONLY Ex) speed, mass, energy, density, distance, temperature, current, pressure; 3m, 900calories, 7 o C
 * Vectors: Magnitude and a direction Ex) velocity, force, weight, acceleration, displacement; 3m North, 7m/s East
 * Some Properties of Vectors; 1. can be manipulated algebraically, 2. can be combined graphically or by calculation

__Addition of parallel vectors.__
The resultant vector must have magnitude and direction.
 * Two Vectors in the same direction; The resultant force is the a__ ddition __ of two vectors acting in the__ same __ direction.
 * Two Vectors in the opposite direction; The resultant force is the addition of two vectors acting in t__ owards __ the bigger force's direction.

__Addition of non-parallel vectors using the parallelogram method__
The resultant force is represented by the diagonal of the parallelogram. It also gives us the direction of the resultant force.

__Addition of non-parallel vectors using the tip-to-tail method__
The resultant force is found by joining the start point of a force to the end point of another force. A triangle is thus formed and the resultant force can be measured.

1.5.1 Effects of forces • Recall and use the relation between force, mass and acceleration (including the direction), F = ma
 * Supplement **
 * • Describe qualitatively motion in a circular path due to a perpendicular force (F = mv ** 2 ** /r is not required) **

**Circular motion**
Any object moving along a circular path is **changing direction** as it goes. An object following a circular path is acted on by a force at right angles to its velocity. (__Fig A and B on your text page 48)__ TASK 1: The diagram shows a particle moving anticlockwise in a circle at constant speed. Indicate the direction of its velocity, v, and its acceleration, a, when it is at point blue. [|Image] from www.physicsclassroom.com from [|www.honolulu.hawaii.edu] For an object in uniform circular motion, the speed is always the same but the __ direction __ is always changing. As a result, the velocity is always changing and thus, the object is __ accelerating __.

<span style="font-family: Arial,sans-serif;">The **inward** force needed for this circular motion is called **centripetal** force. The direction of centripetal acceleration is always changing and towards the centre of the circular path and the its size is constant. This force is increased if: <span style="font-family: Arial,sans-serif;">1) the mass of the object is increased <span style="font-family: Arial,sans-serif;">2) the speed of the object is increased <span style="font-family: Arial,sans-serif;">3) the radius of the circle is decreased

1.5.1 Effects of forces LOs • Recognise that a force may produce a change in size and shape of a body • Plot and interpret extension-load graphs and describe the associated experimental procedure
 * Supplement **
 * • State Hooke’s Law and recall and use the expression F = k x, where k is the spring constant **
 * • Recognise the significance of the ‘limit of proportionality’ for an extension-load graph **

** Classwork Task **
<span style="background-color: #ffffff; color: #58646d; font-family: &#39;Helvetica Neue&#39;,&#39;Lucida Grande&#39;,&#39;Segoe UI&#39;,&#39;Trebuchet MS&#39;,Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">Click one of the Hooke's law simulations below and do an experiment to find the spring constant of a spring. <span style="background-color: #ffffff; color: #58646d; font-family: &#39;Helvetica Neue&#39;,&#39;Lucida Grande&#39;,&#39;Segoe UI&#39;,&#39;Trebuchet MS&#39;,Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">1. Plot a graph showing extension vs load using your results table. <span style="background-color: #ffffff; color: #58646d; font-family: &#39;Helvetica Neue&#39;,&#39;Lucida Grande&#39;,&#39;Segoe UI&#39;,&#39;Trebuchet MS&#39;,Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">2. Add the line of best fit. <span style="background-color: #ffffff; color: #58646d; font-family: &#39;Helvetica Neue&#39;,&#39;Lucida Grande&#39;,&#39;Segoe UI&#39;,&#39;Trebuchet MS&#39;,Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">3. <span style="background-color: #ffffff; color: #58646d; font-family: "Helvetica Neue","Lucida Grande","Segoe UI","Trebuchet MS",Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">Determine/explain the relationship beween them ( Using the slope of your graph, calculate the spring constant 'k'- you need to show your working ). <span style="background-color: #ffffff; color: #58646d; font-family: &#39;Helvetica Neue&#39;,&#39;Lucida Grande&#39;,&#39;Segoe UI&#39;,&#39;Trebuchet MS&#39;,Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">4. State Hooke's law on the same graph paper and submit your work to Ms. Lee before the end of class. <span style="background-color: #ffffff; color: #58646d; font-family: &#39;Helvetica Neue&#39;,&#39;Lucida Grande&#39;,&#39;Segoe UI&#39;,&#39;Trebuchet MS&#39;,Verdana,Arial,Helvetica,sans-serif; font-size: 14px;">When you completed your task, do workbook pages 19 - 21.

media type="custom" key="29555427"
[|Hooke's law] Phet Colorado edu [|Hooke's law simulation] from cdac.olabs.edu

Hooke's Law
The __e xtension __ of a spring is directly proportional to the __ force __ applied to it, provided the elastic limit is not exceeded.
 * ==F = - //k x//== || **F** is the __restoring__ force of a spring.


 * //x//** is displacement from equilibrium

1: Hooke's law holds only within certain limitations. 2: Negative indicates the direction of the force || Example questions: Example 1) A mass m stretches a spring a distance x. How far will 5m stretch it? 5 times Example 2) A 300g mass stretches a spring 50cm. What is the spring constant? F = -kx, (300g x 10m/s2 ) = -k (50cm), (0.3kg x 10m/s2) = -k (0.5m), k= -6 N /m Example 3) How far will a force of 6 x 10 3 N stretch a spring with spring constant 3 x 10 4 N /m?
 * //k//** is spring constant [ unit: N/m ] ||
 * Be aware the points below;

Hooke’s law ( The __e xtension __ of a spring is directly proportional to the __ force __ applied to it ) is valid only up to the proportionality limit of a material. Beyond this limit, Hooke’s law no longer applies. Beyond the elastic limit, the material remains deformed even when the stress is removed.

•The material no longer shows elastic behaviour (ie The spring does not return to original size when stretching force is removed) •The material is permanently deformed ie The spring is larger or longer than originally •The material is weaker as the above effects are caused by fracture of some atomic bonds
 * Elastic limit:**

<span style="color: #0000ff; font-family: &#39;ComicSansMS&#39;; font-size: 10.6667px;">Image from [|physconcepts]

**Application:** Deformation of materials is also critical in vehicle design though in practice the terms stress ( the force per square metre ) and strain ( the extension per unit length ) are more commonly used instead of simply force and extension; strain is directly proportional to stress. <span style="display: block; line-height: 0px; overflow: hidden; text-align: left; vertical-align: baseline;"> [|Head STEAM] Published on 17 Apr 2014 ||
 * media type="youtube" key="hJHaov5CT-o" width="560" height="315" || media type="youtube" key="PgPR8Q4DbOM" width="560" height="315" ||
 * [|Hooke's Law Sample Problem, Chapter 14 Review] [|dcaulf] Published on 27 Mar 2012 || [|How long is a spring?] | Physics and Forces | Fran Scott | Head STEAM


 * Hooke's law ** **from Britannica**
 * Hooke's law** **from BBC GCSE Bitesize**

<span style="font-family: &#39;Times New Roman&#39;; font-size: 14.6667px;">Forces and elasticity questions from BBC GCSE Bitesize

media type="custom" key="29555429" [|Hooke's law and petential energy] Phet Colorado Edu

<span style="font-family: &#39;Comic Sans MS&#39;;">1) Explain Newtons first law of motion. <span style="font-family: &#39;Comic Sans MS&#39;;">2) What is the unit of measure for force? <span style="font-family: &#39;Comic Sans MS&#39;;">3) How is mass converted in to 'weight’ ? <span style="font-family: &#39;Comic Sans MS&#39;;">4) A 25Kg sack of potatoes is lifted in to a 2M high shelf. What is the weight of the sack and how much work is done on it? <span style="font-family: &#39;Comic Sans MS&#39;;">5) Write down the formula for momentum. <span style="font-family: &#39;Comic Sans MS&#39;;">6) A cart is travelling at 20m/s. Its mass is 500Kg. What is the cars momentum? <span style="font-family: &#39;Comic Sans MS&#39;;">7) A car has a momentum of 200Kgm/s. It turns left…explain how it’s momentum changes. <span style="font-family: &#39;Comic Sans MS&#39;;">8) Suggest 5 things that could affect braking distance. <span style="font-family: &#39;Comic Sans MS&#39;;">9) Suggest 5 things that could affect thinking distance. <span style="font-family: &#39;Comic Sans MS&#39;;">10) A driver has a reaction time of 0.5 seconds. What is the thinking distance if she is driving at 30m/s? <span style="font-family: &#39;Comic Sans MS&#39;;">11) A car of 500Kg at 10m/s travelling east to west, crashes in to a car travelling west to east. The second car has a mass of 750N and is travelling at 5m/s. On impact the first car comes to a halt. What happens to the second car? <span style="font-family: &#39;Comic Sans MS&#39;;">12) Write down and explain Newtons second law of motion. <span style="font-family: &#39;Comic Sans MS&#39;;">13) A force of 600N is used to push an asteroid of mass 200Kg. What is the acceleration of the asteroid? <span style="font-family: &#39;Comic Sans MS&#39;;">14) An car engine produces a force of 1500N. Friction opposes motion with a force of 750N. The vehicle mass is 600Kg. What is the acceleration. <span style="font-family: &#39;Comic Sans MS&#39;;">15) Write down Newtons third law of motion. <span style="font-family: &#39;Comic Sans MS&#39;;">16) Explain in terms of the forces, why a parachutist reaches a terminal velocity before and after she opens her parachute.
 * <span style="font-family: &#39;Comic Sans MS&#39;;"> __FORCE__ **
 * __<span style="font-family: &#39;Comic Sans MS&#39;;">TRY AS MANY AS YOU CAN. 10 MINIMUM __**

Forces revision from BBC GCSE Bitesize

1.5.2 Turning effect • Describe the moment of a force as a measure of its turning effect and give everyday examples • Understand that increasing force or distance from the pivot increases the moment of a force • Calculate moment using the product force × perpendicular distance from the pivot • Apply the principle of moments to the balancing of a beam about a pivot Supplement • Perform and describe an experiment (involving vertical forces) to show that there is no net moment on a body in equilibrium • Apply the idea of opposing moments to simple systems in equilibrium

1.5.3 Conditions for equilibrium • Recognise that, when there is no resultant force and no resultant turning effect, a system is in equilibrium Supplement • Perform and describe an experiment (involving vertical forces) to show that there is no net moment on a body in equilibrium Image from [|www.universalhub.com/2016] || Image from[| www.mirror.co.uk] || **Turning effect of forces (Moment )** Experiment: Turning Effect of Forces Balancing a beam. **Moment: The measure of its turning effect of a force about a pivot.**
 * [[image:crane collapsed.jpg width="558" height="387"]]

Moment = force x perpendicular distance from pivot to force = __ //F// x //d// __ The SI unit of **__the moment of a force__** is the__ newton metre __ [__ N m __]. The moment (Turning effect) describes with __ magnitude __ in N m and __ direction __ as clockwise or anticlockwise. 1. The moment of a force is bigger if the force is __ bigger. __ 2. The moment of a force is bigger if it acts __ further __ from the pivot. 3. The moment of a force is the greatest if it acts at 90 o to the object it acts on.
 * where //F//= force [in N]
 * //d// = perpendicular distance from pivot [in m]

When a system is in equilibrium, the resultant force is __ zero __ and the resultant turning effect is __ zero. __
 * Total clockwise moment = Total anticlockwise moment.

Equilibrium: the state of being balanced due to the zero resultant force.

Law of the lever.mp4

**Question A** A student conducts the following experiment on a half-metre rule to feel the turning effect of a force (a) If the weight W is placed at the 15cm mark to the left from 0 cm mark, find the moment of the force applied by a hand when holding the ruler horizontally at the position between 40 cm and 50 cm to the far left. (b) He then shifts the same weight W to the 5 cm mark and finds that it is more difficult now to maintain the half-metre rule in a horizontal position than before in (a). Why is this so?

Question B An object is in constant motion. There are a number of forces acting on the object. State the two conditions which must apply for the body to remain at the same constant motion. 1. No resultant force in any direction or No net force in any direction 2. No net moment or No turning effect or No torque or Total clockwise moment is equal to total anticlockwise moment

**Homework** [|Pivots and Levers] and [|Calculating Moments] from Intel Education Do questions on your Revision p.28

=Exit ticket: //Write 3 things you learnt during the class today in your notebook, while watching the video clip 'The lever'//= media type="youtube" key="Us2KfO_yrPA" width="560" height="315" [|Eureka! Episode 12 - The Lever] 1.5.4 Centre of mass • Perform and describe an experiment to determine the position of the centre of mass of a plane lamina = • Describe qualitatively the effect of the position of the centre of mass on the stability of simple object = =Which way it would collapse?= = Image from creating-wonder.blogspot.com/2014/04/ = [|Balancing Soda Can] scienceprojectideasforkids.com

A single point at which the whole mass of the body or system is imagined to be concentrated and all the applied forces acts at that point. T<span class="hvr" style="background-color: #ffffff; color: #1d4994; font-family: Arial,Helvetica,sans-serif;">he <span class="hvr" style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;">point <span style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;"> at <span class="hvr" style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;">which the mass <span style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;"> of a <span class="hvr" style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;">system could <span style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;"> be <span class="hvr" style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;">concentrated without affecting the behaviour <span style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;"> of <span class="hvr" style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;">the system under the action <span style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;"> of <span class="hvr" style="background-color: #ffffff; color: #404040; font-family: Arial,Helvetica,sans-serif;">external linear forces. Centre of gravity and Centre of mass are the same, when the object is in a uniform gravitational field. When drawing two vertical lines from the pin points across the lamina toward the centre of gravity, the point where lines cross is the centre of mass. The position of the centre of mass affects the __stability__ of an object. The **lower** the centre of mass, the more __stable__ the object becomes.
 * Centre of mass:** The point in the body where all the mass acts.

[|How to find the centre of mass] from BBC GCSE Bitesize [|Stability] from schoolphysics.co.uk image from www.udemy.com/physics-moments-turning-effect-of-forces/ [|Revise Moment and Cantre of Mass] from www.gcestudybuddy.com
 * Challenge:** Where is the centre of mass located in a torus?

Sometimes the center of mass doesn't fall anywhere on the object. The center of mass of a ring for example is located at its center, where there isn't any material. [|What is centre of mass?] from www.khanacademy.org

1.6 Momentum From 1.5.1 • Recall and use the relation between force, mass and acceleration (including the direction), F = ma <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">NEWTON’S FIRST LAW OF MOTION: A body continues to maintain its state of rest or of uniform motion in a straight line unless acted upon by an external unbalanced force.
 * Supplement **
 * • Understand the concepts of momentum and impulse **
 * • Recall and use the equation momentum = mass × velocity, p=mv **
 * • Recall and use the equation for impulse Ft = mv – mu **
 * • Apply the principle of the conservation of momentum to solve simple problems in one dimension **
 * Newton’s first law of motion.**

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 12px;">TRANSLATIONAL EQUILIBRIUM: When the net force on an object is zero in all directions (ie no linear acceleration). =** Newton’s second law of motion. **= F = ma can be expressed as F = Δp/Δt = = <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 12px;">NEWTON’S SECOND LAW OF MOTION: ∑F = ma The rate of change of momentum of an object is proportional to the applied force and takes place in the direction in which the force acts. = =
 * Condition for translational equilibrium.**

== = = NEWTON’S THIRD LAW OF MOTION: Whenever a particle A exerts a force on another particle B, B simultaneously exerts a force on A with the same magnitude in the opposite direction. When two bodies A and B interact, the force that A exerts on B is equal and opposite to the force that B exerts on A.
 * Problems involving Newton’s second law.**



<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif;">LINEAR MOMENTUM: the product of mass and velocity. It is a vector measured in kgms <span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; vertical-align: super;">-1 Momentum can be thought of as how difficult it would be to stop a moving object.

<span style="background-color: #ffffff; font-family: Arial,Helvetica,sans-serif; font-size: 12px;">IMPULSE: The change in momentum. A vector. Unit is Ns Impulse **due to a time-varying force by interpreting a force–time graph.** <span style="background-color: #ffffff; font-family: &#39;Times CY&#39;;">LAW OF CONSERVATION OF LINEAR MOMENTUM: The momentum of an isolated system remains constant (ie when no external forces are acting). Or, in any isolated system, the change in momentum is zero. The total momentum of a system remains constant before and after a collision. There are 2 types of collision: m1v1 + m2v2 = (m1 + m2) v || 2)Rebound = when the objects bounce off each other: (m1v1 + m2v2)BEFORE = (m1v1 + m2v2)AFTER || Do all the practice questions! <span style="display: block; height: 1px; left: 0px; overflow: hidden; position: absolute; top: 8839.5px; width: 1px;"><span style="font-family: Arial,sans-serif; font-size: 24pt; line-height: 107%;">The bigger the mass of the same size and shape, the harder to change its motion. <span style="font-family: Arial,sans-serif; font-size: 24pt; line-height: 107%;">Weight <span style="font-family: Arial,sans-serif; font-size: 24pt; line-height: normal; margin: 6pt 0cm 0cm;">The effect of gravity on a mass. It is the product of a mass and acceleration due to gravity. <span style="display: block; font-family: Arial,sans-serif; font-size: 24pt; line-height: normal; margin: 6pt 0cm 0cm; text-align: center;">W = mg <span style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0cm; margin-left: 0cm; margin-right: 0cm; margin-top: 6.0pt;"><span style="font-family: Arial,sans-serif; font-size: 24pt;">Weight - Newtons (N) mass - kilograms (kg) acceleration due to gravity - meters/second/second (m/s <span style="font-family: Arial,sans-serif; font-size: 20pt;">2 <span style="font-family: Arial,sans-serif; font-size: 24pt;">)
 * Impulse **can be found by calculating the **area** **under** a Force-time graph.
 * The law of conservation of linear momentum.**
 * [[image:Momentum coupled.jpg]] || [[image:Momentum rebound.jpg.gif width="301" height="260"]] ||
 * 1)Coupled = when the objects are stuck together after impact: