KS3+Forces+and+motion

media type="youtube" key="FiZqn6fV-4Y" width="560" height="315" [|Louie Schwartzberg: Hidden miracles of the natural world] from youtube.com
 * Forces and their effects **


 * Homework**
 * 18 Feb. 2013: All the students who come back to school later should complete the questions on the Science workbook3 p54 ~p58.**
 * Here you can find the pages.**

understand that forces change the speed and direction of objects measure forces investigate the effect of forces on the shape of objects understand balanced forces understand the effects of friction __You have 10 minutes to finish the worksheets given to you.__ =Forces= Brainpop [|force] A force is a __ push __ or a __ pull __ in a particular direction. Forces always acts in pairs. Forces can push or pull in any direction and more than one force can act on an object at a time.

Forces cause acceleration since it changes in the __ speed __ or __ direction __ of an object. Forces usually cannot be seen but their effects can.Forces can be measured in Newtons. The SI unit of force is__ newton __ [__ N __]. A force of 10N is roughly the amount of force the Earth's gravity pulls on a 1 kg mass.

**What is the effect of a force on motion?**
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 decrease speed. 4. A force can cause a moving object to __ change __ its __ direction __ of motion. Forces from Brain pop 1. Forces always occur in __ pair __s. Each pair is made of an __ action __ force and a__ reaction __ force. 2. Action and reaction forces are equal in __ magnitude __. 3. Action and reaction forces act in__ opposite __ directions.

1. contact force 2. Weight 3. [|Friction]: A force that occurs between two surfaces rubbing against each other. from Intel education : The opposition to the motion acts in contact. The resistance caused by any two objects in contact. 4. Tension 5. Resistance Air resistance: A frictional force that acts against an object moving through air. Drag. 6. Magnetic force [|Forces activity] from BBC KS3 Bitesize
 * Types of force**

What happens to the object when the forces act depends on 1. __how strong the forces are__ and 2. __the direction of the forces__ that are applied on the object. The combination of all the forces acting on an object is the __ net/resultant __ force. When more than one force acts on an object, the forces combine to form a net 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.

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 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.) [|Balanced forces] from Intel Education If the effects of the forces don't cancel each other, if one force is stronger than others, the forces are __ unbalanced __. Forces acting on an object that change its speed or direction. [|Forces] from BBC bitesize Resultant force Thrust Upthrust Streamlined Weight || The force of attraction between any two objects that have mass. A single force that has the same effect as all the forces acting on an object added together. A force that pushes an object forwards. A force that pushes an object upwards. A smooth shape designed to reduce drag. Earth gravitational force: The force of attraction that pulls objects towards the contre of the Earth. It is measured in Newton(s). ||
 * Balanced forces;**
 * Unbalanced forces** cause a change in motion; speed, direction
 * Keywords || Definitions ||
 * Gravitational force

Measuring forces
A **newtonmeter**/**forcemeter** is an instrument that is used to measure forces. __Aim(1):__ To measure the size of a force using a newtonmeter. __Apparatus(1):__ __Diagram(3):__ __Method(2)__ 1. Copy the result table below and make a list of objects. 2. Find a size of the force applied to drag an object. 3. Repeat measuring the size of a force for each object. 4. Find the average size of the force for each object.

__Results(2)__ 2. 3. 4. 5. 6. 7. 8. 9. || a 10g mass a 50g mass a 100g mass a ruler an eraser a pencil case a book a shoe your choice ||  || __Conclusion(1)__ Write down your opinion based on the relationship that you found from your result 1 to 3. 1. How many grams is equal to 1 Newton from your results? 2. Can you tell me how many kilograms is in 1 Newton? 3. What is the relationship between mass and force? 4. Can you guess what are the masses of your objects? 5. According to the Newton's 2nd law of motion, F [N]= m [kg] x a [N/kg]. Can you guess what is the acceleration applying to a mass on Earth?
 * No || Object [g] || Force [N] ||
 * 1.

__Evaluation__ Is your test fair? What can you do to improve your practical and to make it a fair test?

Quiz: 1. Which statement is correct? A. Mass is a force, measured in kilograms. B. Mass is a force, measured in newtons. C. Weight is a force, measured in kilograms. D. Weight is a force, measured in newtons.

2. Which statement about the mass of a falling object is correct? A. It decreases as the object falls. B. It is equal to the weight of the object. C. It is measured in newtons. D. It stays the same as the object falls.

3. Below are four statements about the effects of forces on objects. Which statement is incorrect? A. A force can change the length of an object. B. A force can change the mass of an object. C. A force can change the shape of an object. D. A force can change the speed of an object.

4. What is the gravitational force that the Earth exerts on an object? A. the density of the object. B. the mass of the object. C. the volume of the object. D. the weight of the object.

Scalar : Physical quantities that have __ magnitude __ only. ex) Mass, Distance, Speed Vector: Physical quantities that have both magnitude and __ direction __. ex) Force(Weight), Displacement, Velocity
 * Extension:
 * Scalar and Vector**

**Adding forces**; Is force a scalar or a vector quantity?
Find a single vector that will produce the same effect as the two vectors added together in both magnitude and the direction of the vectors. This single vector is called the resultant vector.

__Addition of parallel vectors.__
The resultant vector must have magnitude and direction. 2 Vectors in the same direction; The resultant force is the a__ ddition __ of two vectors acting in the__ same __ direction. 2 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. See Fig. 3.13 on page 51.

__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. See Fig. 3.15 on page 51. media type="youtube" key="1Tv6BnXzzg4" width="447" height="250" [|Relative Motion Problem: Solving for the angle of the moving object] from youtube.com

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. Do you remember what Terminal Velocity is? Skydiving

Newton's laws of motion

__Newton's First Law of Motion__ When forces are balanced =>> Accleration= 0 m s -2 -> Object at rest will remain at__ rest __, Object in motion will remain in motion at__ constant __ velocity

__Newton's Second Law of Motion__ When a resultant force acting on an object of constant mass is not zero, => Forces are __ unbalanced __ -> The object will accelerate and move in the direction of the resultant force. The product of the mass and acceleration of the object is equal to the resultant force.;__ F = ma __ ex) Weight on Earth is a force; F= mg

A truck engine of mass 5000 kg is pulling a trailer of mass 1000 kg along a level track at an acceleration of 0.10 m s -2. The resistances are 10 N per 1000 kg for the truck engine and 5 N per 1000 kg for the trailer. (a) Draw a free body diagram of the engine and the trailer (b) Calculate the tension in the connection tow bar between the engine and the trailer. (c) Calculate the forward thrust exerted by the engine.
 * Question A**

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?
 * Question B**

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 C **

__Newton's Third Law of Motion__ For every action, there is an equal and opposite reaction and these forces act on mutually opposite bodies. 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. Fill in the blanks Aerodynamics, Streamline aerofoil ||
 * Find the definition of below words and check the principal of airplane wings.

** Forces summary ** A force is anything that makes an object __** accelerate **__. Speed tells you how __** fast **__ you're going and it is measured in a unit of distance per unit of time, like meters per second or kilometers per hour.

__ Acceleration __ is the __** rate **__ at which velocity changes, and it is measured in velocity per unit of time.

If you are speeding up an extra 5meters per second every second, you are accelerating at 5 meters per second per second, or 5 meters per second squared and your acceleration is a positive number. If you are slowing down, the acceleration will be a __** negative **__ number, like -5 (negative five) meters per second squared. Acceleration in the direction of motion speeds you up, and acceleration in the opposite direction of motion slows you down. So, you can see the minus here telling you the __** direction **__ of the acceleration. Anything that causes an object to speed up (positive acceleration), to slow down (negative acceleration) or to change direction is a force. When you are not changing your speed, acceleration is __** zero **__.

Earth's gravity causes objects to accelerate towards it at approximately __ 9.8 meters per second squared __.

An object in motion will stay in __** motion **__, and an object at __** rest **__ will stay at rest unless ** unbalanced ** force acts on it (Inertia). An object's forward motion will continue until an unbalanced force acts in the opposite direction to stop it. When you are in a moving car, the seat belts provided the unbalanced force that stopped out bodies from moving forward it.
 * Newton's first law of motion.**

An object that has unbalanced force acting on it will __** accelerate **__ in the direction of that force.
 * Newton's second law of motion: F = ma**

//Weight = mass  x gravity // The **gravitational field strength** //g// is the force per unit mass acting on //m// due to the presence of //M(Earth's mass)//. The units are newtons per kilogram ( N/kg ).

Forces always occur in __** equal **__ and __** opposite **__ pairs.
 * Newton's third law of motion**

Calculate average speeds, including through the use of timing gates. measure speed and calculate average speed produce distance-time graphs interpret gradients on distance-time graphs interpret changes of gradient on distance-time graphs [|Speed, distance-time graphs] from BBC GCSE bitesize [|Speed test] from BBC GCSE bitesize

=Experiment on speed(20 marks)= Aim: To calculate average speed by investigating the relationship between speed and a gradient of a distance and time graph. Apparatus(1): Diagram(1): Method(2): Results(12): > Title, Labelled axes, Units, Proper scale, Correct data plotted, Legend, Line of best fit, Triangular method is shown to find the gradient. Formula of speed presented and correct calculation. Conclusion(2): Analyse the distance vs time graph. 1. What does the gradient of your graph tell you? 2. What is the relationship between the gradient and speed? Evaluation(2): 1. Is your experiment fair? 2. How can you improve the experiment?
 * Table required with units(2)
 * Graphs plotted on graph paper attached(10):
 * Interpret the distance vs time graphs

Gear you up. You will run as fast as you can. You may need pants or shorts on Tuesday for G7 Ruby and on Friday for G7 Amber. Enjoy your running.

consider acceleration and braking What is an acceleration? Write down your understanding from your research and make a poster. Include examples showing acceleration.

**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) understand the relationship between gravity and weight investigate gravity and the planets Gravity : Gravitational field strength. It varies depending on the mass of a planet. ex) Copy the table of the different gravitational field strength in solar system in your text p.212 Weight : Force of gravity. It is a force of attraction between masses. The gravitational force of an object depends upon their __ masses __ and the distance between them. It pulls things towards the __ centre __ of the mass. Mass: It shows how much substance is in an object. F = m x a || . where, || **F** is force of gravity. Gravity 3: Write three facts or concept you knew before watching each video clip. You may want to read questions given below to have some ideas on what to think. 2: Write two things you discovered or learnt from each video clip while watching them. 1: Write one concept or a question you would like to know more about.
 * m** is mass.
 * a** is the gravity ||
 * 3-2-1 Activity:**

Q1. What is gravity? Q2. What are the factors that affect the magnitude of gravity? media type="custom" key="27964435" GRAVITY VISUALIZED from youtube.com Q3. Why do you think those balls all stopped eventually? Q4. What would happen if this experiment is conducted in the universe not on a piece of fabric? Q5. What would happen if the sun disappeared in our solar system? media type="custom" key="27964437" [|GRAVITY - Newton to Einstein] from youtube.com

Q6. What is inertia? media type="youtube" key="9cPGj8yyJD0" width="560" height="315" EUREKA [|EPISODE 1 INERTIA] from [|Vincent Salij] Published on 29 Nov 2012 youtube.com

Q7.What is mass? media type="custom" key="27964433" EUREKA EPISODE MASS from youtube.com

<span style="background-color: #ffffff; font-family: &#39;Lucida Sans&#39;,&#39;Lucida Grande&#39;,&#39;Lucida Sans Unicode&#39;,Verdana,sans-serif;">Q8. Can you tell the difference between mass and weight?

<span style="background-color: #ffffff; font-family: &#39;Lucida Sans&#39;,&#39;Lucida Grande&#39;,&#39;Lucida Sans Unicode&#39;,Verdana,sans-serif;">**TIDES** <span style="background-color: #ffffff; display: block; font-family: "Lucida Sans","Lucida Grande","Lucida Sans Unicode",Verdana,sans-serif;">The periodic rise and fall of sea level caused by gravitational interactions of the sun, moon and Earth. <span style="background-color: #ffffff; font-family: &#39;Lucida Sans&#39;,&#39;Lucida Grande&#39;,&#39;Lucida Sans Unicode&#39;,Verdana,sans-serif;">Some places have one low tide and one high tide per day. Other places have two high and low tides in each day approximately equal in size. The wavelength of an average tide can be up to 17,000 km.

<span style="background-color: #ffffff; font-family: &#39;Lucida Sans&#39;,&#39;Lucida Grande&#39;,&#39;Lucida Sans Unicode&#39;,Verdana,sans-serif;">Spring tides occur when the sun and moon are in a straight line. The tidal range is typically highest during spring tides. <span style="background-color: #ffffff; display: block; font-family: "Lucida Sans","Lucida Grande","Lucida Sans Unicode",Verdana,sans-serif;">Neap tides occur when the sun and moon form a right angle with Earth. <span style="background-color: #ffffff; display: block; font-family: "Lucida Sans","Lucida Grande","Lucida Sans Unicode",Verdana,sans-serif;">Q9. Why is the moon’s pull greater than the sun’s? //**Homework 20th Feb. 2013:**// 1. Take a note on the relationship between gravity and weight after reading your text (Science1) p.212 and by researching the below websites. [|Force Gravity and Weight from BBC GCSE BITESIZE] [|Gravity and Weight from Newton's homepage] [|Planet from BBC BITESIZE] 2. List the planets on our solar system by the sequence of the size of the gravity of each planet.media type="youtube" key="zR3Igc3Rhfg" width="560" height="315" [|To Scale: The Solar System] [|To Scale:] Published on 16 Sep 2015

**__Investigation on Hookes' law__**
Aim: To investigate how the amount of mass affects the extension of a spring __// Safety: What are the dangers here? Is there an eye hazard? You need to make sure that you do everything possible to reduce the risk of harm. //__ What to do: Measure the length of each spring when it is not stretched. Now measure the lengths of the springs when they are hooked and stretched gently. Work out how much each spring has stretched. The amount of stretch is called the extension. Do the springs have the same extension? Hang one of the springs from a stable stand. Measure the length of the spring and record it. Hang one mass from the spring. Work out extension. Repeat this for the other spring. Do they have the same extension now? Choose one of the springs and hang it from the stable stand. Hang different numbers of masses from the spring. Measure the length of the spring and work out its extension each time. Put your results into a table below. Results table: What is your idea?

Know that forces can cause objects to turn on a pivot and understand the principle of moments.
 * Moment **

Moment: The turning effect of a force around a fulcrum.
Moment of a force = __ //F// x //d// __ where //F//= force [in N] and //d// = perpendicular distance from the pivot [in m]

The SI unit of the moment of a force is the__ newton metre __ [ __ Nm __]. The moment of a force describes with __ magnitude __ in N m and the __ direction __ as clockwise or anticlockwise. The sum of the clockwise moments about any point (such as fulcrum) equals the sum of the anticlockwise moments about the point. Examples) See-saw, Pliers, Scissors

Moment experiment results table
 * Left || mass [kg] || force [N] || distance[m] || anti clockwise Moment [Nm] ||  || Right || mass [kg] || force [N] || distance[m] || clockwise Moment [Nm] ||
 * Trial 1 ||  ||   ||   ||   ||   || Trial 1 ||   ||   ||   ||   ||
 * Trial 2 ||  ||   ||   ||   ||   || Trial 2 ||   ||   ||   ||   ||
 * Trial 3 ||  ||   ||   ||   ||   || Trial 3 ||   ||   ||   ||   ||
 * Trial 4 ||  ||   ||   ||   ||   || Trial 4 ||   ||   ||   ||   ||

[|Pivots and Levers] and [|Calculating Moments] from Intel Education Do questions 4~6 on your text Science3 p.192.

**Pressure in liquids and gases**