KS3 Science Forces 2

KS3 ScienceForces 2

Name: _____________________________Class: ___________________________Teacher: ____________________

In this topic you will learn about:• Contact and non-contact forces• Elastic properties and Hooke’s Law• Pressure in solids, liquids and gasses• Sinking, floating and upthrustPractical Skills: • GCSE RP– Hooke’s lawThis will prepare you for:• GCSE physics topic ‘Forces A & Forces B’This topic has links to• Particle model of matterMaths in science: • Rearranging Equations• Plotting Graphs

Key Words:ForceEquilibriumResultantStreamliningStretchingCompressionPressureFluidsSolidsLiquidsGassesBuoyancyUpthrust

Contents:

Booklet Expectations:

The booklet is your responsibility to look after and keep tidy.

You are expected to bring the booklet to every lesson with that class teacher.

Any corrections / self assessment to be completed in green pen, as indicated by your class teacher – Or when you see the ‘feedback & assessment’ logo

Any response to marking and literacy codes to be completed in green pen.

Any diagrams are to be drawn in pencil, graphs using a pencil and ruler etc.

All activities are to be completed, including homework, to the best of your ability, and corrected where needed.

When reading through the notes, you are expected to highlight any words you do not understand, then write their definitions on the glossary pages at the back of the booklet.

Lesson 1: EquilibriumLesson 2: DragLesson 3: Stretch and Compression Lesson 4: Investigating Extension Lesson 5: Pressure on SolidsLesson 6: Pressure in FluidsLesson 7: Sinking and FloatingRevision

Week commencing 7th DEC – 11th Jan2 Lessons per week

Lesson 1: Equilibrium

In and On: Why don’t planes fall out of the sky?

Learning outcomes:• Identify forces and their directions• Describe how opposing forces can

result in equilibrium• Calculate resultant force

What 3 things can a force do?________________________________________________________________________

Key Words:

1) Contact force: A contact force is a force that occurs when objects are

touching E.g. friction or applied force

2) Non-contact force: a force which acts on an object without coming

physically in contact with it. E.g. Magnetism and gravity

Balanced forces: Arrow diagrams:Add arrows to the diagram to show:

a) Forces acting on a person sat on a chair

b) Forces acting on a plane flying at constant speed and height

b) A gymnast balancing on a beam

Define the term‘equilibrium’

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Challenge: Explain how the forces on the gymnast would be different if the person was heavier?

Weight is pulling you down

The chair is pushing back up on you

Weight pulling the plane down

Lift pushing the plane up

Scan Me

In the following situations the forces are in equilibrium. Identify the forces involved when: 1. a person is lying on a mattress ____________________________________________________________________________________

2. a person is standing on some bathroom scales _________________________________________________________________________

3) a jacket is hanging on a hanger _____________________________________________________________________________________

If we have multiple forces acting on an object, we can calculate a resultantforce. A resultant force is a single force that has the same effect on theobject as all the individual forces acting together.

Task: Calculate the resultant force on each car. State what will happen to its speed.

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b)

c)

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b) ________________________

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c) ________________________

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This car is travelling at steady speed. Calculate the size of the missing force, draw an arrow to show the direction and suggest what it might be

Plenary: Complete the table to show the effect balanced and unbalanced forces can have on speed, direction and shape.

Additional notes:________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Learning outcomes review:

• Identify forces and their directions• Describe how opposing forces can

result in equilibrium• Calculate resultant force.

Key Vocab:

Stays constant Changes – object speeds up or slows down

Stays constant

Changes direction

Scan Me

Lesson 2: DragIn and On: Describe the shape of the images on the board. Why are they shaped like that?

Learning outcomes:• Describe the effects of drag on objects as they move• Describe factors that affect the size of drag forces• Evaluate how well technology reduces drag forces

Why can’t you move through a solid?

Watch the video and answer the following questions:1. In what decade were streamlined cars first sold?

2. Why was a boxy design not a problem in America in the 1960s?

3. How did the price of fuel in Europe compare to the price of fuel in America?

4. How would an aerodynamic, streamlined shape benefit car owners?

5. How and why did the shape of cars change?

Why could a Concorde fly faster than a regular aeroplane?

Sometimes drag can be a good thing…..Challenge: : What happens to an aeroplane’s flaps during landing?

Scan Me

Friction is a resistive force that acts between solid surfaces.

In a fluid (a substance that will flow – liquids or gases) this resistive force is called drag.

The particles in a l____ are packed more closely together than in a ___–we can say the liquid is more dense. This makes it harder to move through and slows you down.

Task 1: Streamlining:Suggest why streamlining is an advantage for each of these:a) a championship diver diving from a great height

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_______________________________________________________b) a jet airliner

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c) a shark

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_______________________________________________________ d) a long-distance cyclist

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Task 2: Design a shapes made from plasticine that:a) Will fall as fast as possible through water Sketch your design & challenge: State why you chose the shapes you did

Imagine you were preparing to do a very fast downhill ski run. As well as needing to be able to ski very well, you also need your equipment and the way you use it to assist.

a) What kind of clothing do you think would help?

b) What kind of position would you adopt, and why?

c) When people are first learning to ski, streamlining isn’t important – why is it more important the faster you go?

Plenary: Write a short paragraph for a magazine about how the clothing,

equipment and strategies used by the British cycling team helped them top the cycling medal table at the Rio 2016 Olympics.



• Describe the effects of drag on objects as they move

• Describe factors that affect the size of drag forces

• Evaluate how well technology reduces drag forces

Key Vocab:

Lesson 3: Stretch and Compression

In and On: Why do mattresses contain springs rather than planks of wood?

Learning outcomes:• Identify the forces involved in changing an object’s shape• Explain what is meant by elastic behaviour• Design an experiment to investigate stretch

If an object goes back to its original shape after being stretched or compressed, we say it exhibits: _______________________________

Annotate the diagrams:

When it won’t go back to it’s original shape we say it is: ___________________

We describe objects that break easily instead of being stretched or compressed as: ___________

1. Give 3 examples of materials which are brittle.

2. Why do cars have suspension systems?

Challenge: Explain why professional tennis players change balls every few games.

An object can be squashed by a compressionforce

An object can be stretched or pulled by a tension force

When something has changed shape, we say it has been deformed

Brittle, Permanently deformed, Elastic behaviour,

Planning a Practical

You have been employed by Jaguar to investigate how the size of a force affects the springs they use in the suspension systems in their cars.Your task is to use the diagram to plan a practical which would help you investigate their query.

Hypothesis:

What do you think will happen if you increase the force on the spring?

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Variables:

Independent Variable:______________________________________________

Dependent Variable: _______________________________________________

Control Variable(s): ________________________________________________

Equipment:•

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•Risk assessment:

Hazard – What could cause harm?

Risk – What harm could it cause?

Prevention – How will you stop the hazard from causing harm?

Important points:

How do you work out a force (weight) from a mass?

How will you work out the extension of the spring?

DiagramDraw a neat pencil diagram of the practical set up you will use.Label the equipment.

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Method



• Identify the forces involved in changing an

object’s shape

• Explain what is meant by elastic behaviour

• Design an experiment to investigate stretch

Key Vocab:

Plenary: 1) Write a tweet to summarise what you have done this lesson

2) Write a second tweet to predict what you will be doing next lesson

Lesson 4: Investigating Extension

In and On: List as many objects as you can think of that exhibit elastic behaviour

Learning outcomes:• Practically investigate the effect of a force on a spring• Explain Hooke’s Law

Hooke's law:The extension of an elastic object is directly proportionalto the force applied

How can you use a graph to identify a directly proportional relationship?

Task: Watch the practical you planned last lesson. Use the results in the video then plot a graph of your results.Complete the conclusion and the evaluation of the practical.

Scan Me

Describe the pattern shown on the graph.Hint: Does it obey hooks law? Did the spring reach its elastic limit?

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Write a conclusion of your results – what did you find?

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Explain knowledge of your findings to Jaguar linked to suspension systems. What would happen if they applied a force too large?_________________________________________________________

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Evaluate the experiment – did anything go wrong? Why? Is your data reliable? How could you improve the practical?_________________________________________________________

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Lesson 5: Pressure on Solids

In and On: What do you think is meant by the term pressure?

Learning outcomes:• Explain what is meant by pressure• Describe effects of varying pressure• Calculate pressure

Pressure is: a measure of how much a force is pushing on something

else.

If the force is applied to a _________ area, the pressure will be _____________. If the force is applied to a _________ area, the pressure will be _____________.

Task: For each picture, state if the feature is designed to increase or decrease pressure

a) An elephants foot having a round base

b) A saw has many tiny teeth

c) Carnivores have long pointy teeth

d) Caterpillar tracks used on snow vehicles

Challenge: Think of your own example of a design to increase / decrease pressure

Smaller, larger, small, larger

Scan Me

Calculating pressure

PRESSURE = FORCE ÷ AREA

Pressure is measured in Pascals (Pa) – this is the same as N/m2.

Task: Complete the questions below:

Where camels stand on very soft sand, they can easily sink into it. Imagine a situation where two different camels, one weighing 4000 N and the other 5000 N, are standing on soft sand where the maximum pressure without sinking is 26 000 Pa.

Calculate the pressure exerted by each camel if they each had a total foot area of 0.2 m2.

Calculate how much load (in N) each camel could carry without sinking.

Describe how a hydraulics system in a car works

Plenary: Design a sports car that could be driven on a muddy field.

Explain how you will make sure it won’t sink and get stuck!

Challenge: Can you make it aerodynamic too?



• Explain what is meant by pressure

• Describe effects of varying pressure

• Calculate pressure

Key Vocab:

Lesson 6: Pressure in fluids

In and On: What is pressure affected by?

Learning outcomes:• Describe how pressure in a liquid changes with depth• Explain pressure changes using the particle model• Describe how pressure in a gas changes with height

Challenge: Do you think pressure will be higher or lower in gasses?

Label on the diagram where the pressure will be high and low. How will that affect how the water comes out of the three holes?

Pressure ___________ with depth. It also acts in all directions

Why do deep sea divers need to wear special suits?

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Describe and explain at which point, A or B pressure will be greatest. Use the key word ‘Particles’ in your explanation.

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Pressure in liquidsPressure is lowest at the top

Pressure is highest at the bottom

Increases or decreases

Pressure in gases

The air is also made of particles. These are pulled to Earth by gravity, resulting in atmospheric pressure.

Will the pressure be higher close to Earth or high up?

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Suggest why some mountain climbers carry oxygen cylinders with them at very high altitudes.__________________________________________________________

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Task: Plot a graph of the data below, which shows how pressure in water changes with depth.

How many pascals (Pa) are in 1 kilopascal (kPa)?

Explain the advantage of using kPa rather than Pa in this case.

Describe the relationship shown by your graph.

Challenge: A student suggested that the pressure at 100 m depth would be 1206 kPa. How confidently can you agree with the student? Explain your answer.



• Describe how pressure in a liquid changes with depth

• Explain pressure changes using the particle model

• Describe how pressure in a gas changes with height

Key Vocab:

Plenary: Complete the sentences below:

a) The pressure at the surface of a swimming pool is _______ than the pressure at a depth of 10 m.

b) A sealed plastic bottle full of air will ___________ if you take it to the bottom of a deep lake.

c) Submarines are built of thick steel because they have to _________ when they dive down deep.

d) Deep sea creatures can die if they are brought to the surface quickly because _______________

Lesson 7: Sinking and Floating

In and On: Why would a piece of wood float but a brick sink?.

Learning outcomes:• Explain why objects float or sink• Describe the forces involved in sinking and floating• Describe how to measure upthrust

Compare the image of the 2 balls. What is the same? What is different?

Density:

Which is more dense, muscle or fat?

If an object is more dense than the liquid it is put in, the object sinks

If an object is less dense than the liquid it is put in, the object floats

Which object(s) would float on water?

Which object(s) would sink?

Task 1: In the diagrams below, sealed boiling tubes are sitting in different liquids. Match the description of the contents to the correct diagram.

Tube containing lead in a beaker of water ____Tube containing water in a beaker of water ____Tube containing water in a beaker of salt water ___Tube containing salt solution in beaker of water ___

Challenge: Explain your answers

When an object is in water, the water provides a ____________ force called __________.

Buoyancy

What will happen if weight is larger than upthrust?

00What will happen if upthrust is larger than weight?

What will happen if upthrust is the same size as weight?

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Answer questions 4, 5 and 6 on page 23 of the textbook.

Answer in full sentences

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Summarise what happens in the video about displacement

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What will happen when the mass is lowered into the water?

Water will be displaced.

What is the upthrust force?

3 N

Plenary: Write a 10 question quiz about the whole forces topic.

Swap with a friend to try each others.



• Explain why objects float or sink

• Describe the forces involved in sinking and floating

• Describe how to measure upthrust

Key Vocab:

Additional notes

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Answers

Lesson 1: EquilibriumIn and on A: The downwards force (gravity) is balancedby the upwards force (lift)

All forces acting on an object balance each other

They would be the same forces, but larger amounts (bigger arrows)

The downward force of the person’s weight; the equal and opposite upward force from the mattress springs.

The downward force of the person’s weight; the equal and opposite upward force from the scales.

The downward force of the coat and hanger’s weight; the equal and opposite upward force from what the hanger is attached to.

500 N to the right. Car will slow down.

2000 N to the left. Car will speed up.

0 N – forces are balanced. Car will travel at steady speed.

Balanced Unbalanced

Speed

Direction

Shape

Stays constant Changes – object speeds up or slows down

Stays constant Changes direction

Stays the sameChanges shape – this is called deformation

Lesson 2: Drag

A: They are streamlined to reduce drag

1930s

The cost of fuel was low

It was much higher in Europe

It would be cheaper because it would waste less fuel

They became curvier to reduce drag

To increase speed and not hurt themselves when they

hit the water

To increase speed and reduce the amount of fuel

needed for the journey

To reduce the energy needed to travel in water, and

allow high speed to catch prey

To increase speed and reduce the energy needed to

travel long distances

Task 2: Design a shapes made from plasticine that:a) Will fall as fast as possible through water Sketch your design & challenge: State why you chose the shapes you did

Imagine you were preparing to do a very fast downhill ski run. As well as needing to be able to ski very well, you also need your equipment and the way you use it to assist.

a) What kind of clothing do you think would help?

b) What kind of position would you adopt, and why?

c) When people are first learning to ski, streamlining isn’t important – why is it more important the faster you go?

Streamlined shape with small area to cut through the water

Close fitting, smooth, light, streamlining body shape

Crouching down – reduces area exposed to the air and minimises drag

At slow speeds there is less drag (you are pushing fewer particles out of the way every second). As you go faster drag increases so you need more streamlining

Lesson 3

In and On: Why do mattresses contain springs rather than planks of wood?The springs in the mattress will compress when you lie on it so it will be comfortable. Wood will not compress so would be very hard and uncomfortable to sleep on.

If an object goes back to its original shape after being stretched or compressed – they show elastic behaviour.

If an object is stretched or compressed too far or too often it won’t go back to its original shape – it is permanently deformed.

Objects that break easily rather than stretch or compress are called brittle.

1. Give 3 examples of materials which are brittle.

2. Explain why professional tennis players change balls every few games.

At the start of the match the tennis balls are elastic, but after being hit repeatedly with very high force they start to become permanently deformed.

Glass, ice, most plastics, ceramics, wood

This is your own prediction

spring

stand

clamp

boss

ruler

masses

force

extensionspring material, strength

spring could

snap

could catch

eyes

wear safety goggles

dropping

masses

injuring foot keep equipment in the centre

of the table

1. Set up the stand, clamp and boss

2. Measure and record the initial length of the spring

3. Hang the spring from the clamp and add 100 g

4. Measure and record the extension

5. Continue adding masses up to 500 g and record

extensions each time

6. Repeat and calculate a mean

Plenary: 1) Write a tweet to summarise what you have done this lesson

2) Write a second tweet to predict what you will be doing next lesson

This should a couple of sentences.

Have a look at the Objectives for next

lesson.

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Describe the pattern shown on the graph.Hint: Does it obey hooks law? Did the spring reach its elastic limit?

Write a conclusion of your results – what did you find?_________________________________________________________

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Explain knowledge of your findings to Jaguar linked to suspension systems. What would happen if they applied a force too large?

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Evaluate the experiment – did anything go wrong? Why? Is your data reliable? How could you improve the practical?_________________________________________________________

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Yes, its directly proportional because it forms a straight line on the graph. But eventually the spring was permanently deformed.

The Spring would be permanently deformed.

Insert any limitations you can think of

For example:

Do we need to measure each weight before using it?

The extension of an elastic object is directly proportional to the force applied until the object is permanently deformed.

Lesson 4 Answers:

Because the graph is a straight line, it shows a linear relationship.

How can you use a graph to identify a directly proportional relationship?

Lesson 5 Answers

If the force is applied to a large area, the pressure will be smaller. If the force is applied to a small area, the pressure will be larger.

The large area reduces the pressure on the ground; this is needed because of the huge weight (force).

The large number of small teeth provides high pressure at the point of each tooth;

The pointed teeth have a small area so create high pressure, which helps the teeth to penetrate the prey.

The tracks cover a larger area than wheels so the pressure on the ground is reduced; this helps to stop the tank sinking into the ground.

In and On: What do you think is meant by the term pressure?a measure of how much a force is pushing on something else.

12 m2

8 m2

6 m2

1.25 Pa

1.67 Pa

0.83 Pa

P = FA

4000N camel - 20,000 Pa

5000N camel - 25,000 Pa

4000N camel – 1200 N

5000N camel – 200 N

The pressure in the 2 pistons is the same.

A small forcepushes down on piston A, which has a small area.

Piston B has a larger area, so the upwards force is bigger than the force on piston A.

The car has large tyres/off road tracks – these increase the surface area to reduce the pressure. Smaller tyres would mean that the pressure would be higher and the car would get stuck in the mud.

Lesson 6 AnswersIn and On: What is pressure affected by?Force and Surface Area

Why do deep sea divers need to wear special suits?

The deeper a diver goes, the higher the pressure will be. This could compress the diver’s lungs, affect blood flow and could damage their body. The suit would reduce the pressure on their body.

We know that liquids are made of particles, and that pressure is caused by a force such as weight.

Will pressure be higher at A or B? Explain why, using the diagram to help.

The pressure will be higher lower down (at B). This is because B has a lot more particles above it, so the weight pushing down will be greater resulting in a higher pressure.

The pressure will be higher closer to Earth where gravity is stronger. The higher up you go, the more space there is between particles so the lower the pressure.

Will the pressure be higher close to Earth or high up?

Use the graph to suggest why some mountain climbers carry oxygen cylinders with them at very high altitudes.

As you climb a mountain, the pressure gets lower. This means there are fewer oxygen particles in every breath you take, so you struggle to get the oxygen your body needs. Having an oxygen cylinder will therefore allow you to breathe if you are struggling or in an emergency.

Plenary: Complete the sentences below:

a) The pressure at the surface of a swimming pool is LOWER than the pressure at a depth of 10 m.

b) A sealed plastic bottle full of air will COMPRESS if you take it to the bottom of a deep lake.

c) Submarines are built of thick steel because they have to WITHSTAND THE HIGH PRESSURE when they dive down deep.

d) Deep sea creatures can die if they are brought to the surface quickly because THEY ARE NOT ADAPTED TO THE LOWER PRESSURE.

How many pascals (Pa) are in 1 kilopascal (kPa)?1000

Explain the advantage of using kPa rather than Pa in this case.The numbers are too large

Describe the relationship shown by your graph.The greater the depth, the greater the pressure

Lesson 7 - Answer

Compare these two balls. What is the same? What is different?

They are the same size (same volume) They have very different masses

In and On: Why would a piece of wood float but a brick sink?.

A piece of wood is less dense than a brick

Which object(s) would float on water?Bamboo woodWhich object(s) would sink?Salt water and mercury

D

Mercury is the densest material so sinks to the bottomA

Same density in the tube and beaker so it will float

C

Lower density in the tube so will float even higher than in AB

Higher density in the tube so sinks (but not as much as D)

The glass and bung of the tube must be more dense than water

When an object is in water, the water provides a buoyancy force called upthrust.

Buoyancy

What will happen if weight is larger than upthrust?

00What will happen if upthrust is larger than weight?

What will happen if upthrust is the same size as weight?

Upthrust

WeightThe object will sink to the bottom

The object will rise to the top and float

The object will not float to the top or sink to the bottom – it will ‘hover’ in the water. This is called neutral buoyancy.

What will happen when the mass is lowered into the water?

What is the upthrust force?

Water will be displaced.3 N

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Summarise what happens in the video about displacement

Water is displaced when an object is lowered into it.The weight of the displaced water is the same size as the upthrust force.

4. How large the upthrust force is: 7 – 4 = 3 N

5.a. The wood is less dense than water

5.b. The water provides upthrust, which partially supports the weight of the steel

5.c. The object displaces water equivalent to its own volume

5.d. The boat is buoyant because it displaces a large volume of water, which gives a large upthrust

6.a. Equal sized upward and downward arrows

6.b. Equal sized upward and downward arrows, bigger than in part a

6.c. Two downward-acting arrows (weight and the downward push) balanced by a large upthrust arrow

6.d. Small downward arrow (weight) and large upthrust arrow

KS3 Science Forces 2

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