Physics 4

Force and Motion

C/W Forces Apr 19, 2023

Aims:- 4 know what forces do

5 explain where forces are balanced

6 apply rules to new situations

• Starter – 2 minutes• In the back of your book, list 5 different

kinds of forces

Copy notes – 3 minutes

• A force is a push or pull on an object• Forces make things

– change speed,– change direction, or– change shape.

• Forces in opposite directions can cancel each other out

Copy diagrams – 5 mins

Pumpkin on a box

Box pushes up on pumpkin

Gravity pulls down on pumpkin

The forces are balanced. The pumpkin doesn’t change speed, shape or direction

Picture Force Diagram

Copy diagrams – 5 mins

Pumpkin in mid-air Gravity pulls down on pumpkin

The forces are not balanced. The pumpkin changes speed – it gets faster, downwards.

Picture Force Diagram

Copy diagrams – 5 mins

Racing car doing 100mph

Engine pushesforward on car

The forces are balanced. The car doesn’t change speed – it stays at 100mph.

Picture

Force Diagram Friction pulls

back on car

Copy diagrams – 5 mins

Racing car doing 100mph

Engine pushesforward on car

The forces are not balanced. The car changes speed – it gets faster.

Picture

Force Diagram Friction pulls

back on car

Your turn – 20 minutes

1. Apple sitting on a table

2. Racing car doing 100mph but with the brakes on

3. Rocket taking off

4. Bungee jumper falling down

5. Bungee jumper being pulled back up

Homework

• Draw a racing car design.

• Label the features that increase the forward force so it can go faster

• Label the features that decrease the backward force (friction and air resistance) so it can go faster

Are You On Target Today?

Aims:-

4 know what forces do

5 explain where forces are balanced

6 apply rules to new situations

C/W Speed Apr 19, 2023

Aims:- 4 know units and formula for speed

5 calculate speed

6 apply rules to changing speeds

• Starter – 2 minutes• In the back of your book, what is missing

here “John’s car goes at 100”

Copy notes – 5 minutes

• Speed is how far you go in a given time• It can be measured in m/s, mph, cm/s etc.• To work out speed remember:-

Steve Digs Turnips

Speed = Distance ÷ Time (m/s) (m) (s)

Calculations – 20 minutes

1. A car goes 50 miles in one hour2. A bus goes 100 miles in 4 hours3. A skateboard goes 2 metres in 1s4. A better skateboard goes 2.5m in 1s5. A skier goes 6m in 2s

A van goes 8km in quarter of an hourA sausage falls 12.76 feet in a week

Practical – 30 minutes

• Listen to instructions• Easy option

– Time the whole length– Repeat for different heights– Record results in a table

• Harder option– Time half way and full length– Record the first half speed and the

second half speed

Plenary – Conclusion

• Easy option– How does the speed depend on the

height of the ramp?

• Harder option– How do the first and second half

speeds compare?– What makes the car speed up?– Draw a force diagram for the car part

way down the ramp

Homework

• No homework this week

Are You On Target Today?

Aims:-

4 know units & formula for speed

5 calculate speed

6 apply rules to changing speeds

C/W FrictionApr 19, 2023

Aims:- 4 give examples of friction

5 explain its good and bad effects

6 use the particle model

• Starter – 2 minutes• In the back of your book, write down three

examples of where friction happens (and are they useful or a nuisance?)

Copy notes – 5 minutes

• Friction is a force between two surfaces• It works to stop things moving• Friction makes energy change into heat• Useful – bike brakes

– The brakes rub on the wheels– The bike’s kinetic energy is changed into heat in

the brake blocks

• Nuisance – inside a machine– The moving parts rub together– Some of the electrical energy working the

machine is turned into heat and wasted

Copy note/diagram – 5 mins

• Air resistance is a kind of friction

• Air particles collide with the moving object and push against it

Air particles (magnified) Air particles hit shuttle nose, pushagainst it and warm it up

Practical – 30 minutes

• Listen to instructions

• Easy option– Time the whole fall– Repeat for different sizes of paper– Record results in a table

• Harder option– As above, plus calculate the speed– Then repeat using double the weight

Plenary – Conclusion

• Easy option– How does the time depend on the size of the

paper parachute?

• Harder option– Is there a relationship between the speed and

the parachute size?– Use the particle idea to explain why doubling

the weight doesn’t make much difference– Draw a force diagram for the paratrooper part

way through the fall

Homework

• There was a good film a few years ago called Terminal Velocity

• Find out what “terminal velocity” means in physics

• EASY – explain it in a couple of sentences

• HARD – explain it using the idea of forces changing and being balanced

Are You On Target Today?

Aims:-

4 give examples of friction

5 explain its good and bad effects

6 use the particle model

C/W Speed GraphsApr 19, 2023

Aims:-

4 describe a journey shown in a graph

5 explain how the graph shows the speed

6 link the graph to the formula for speed

Starter – 5 minutes

• In the back of your book, describe your journey to school – include bits where you stop, go fast, and go slow

Video

“Distance-time set-up”

Copy exampleDistance / m

Time / mins

500

1000

00 10 15 20 25

Walks to school

Stops in shop – whoops,forgot dinner money

Walks fastback home

Oh no, late –runs to school

Questions

1. How does the graph look when you are stopped?

2. How can you tell from the graph if you’re going fast or slow?

3. What does a downward sloping line mean?

4. How can you work out speed from the graph?

Plenary – Your journey

• Sketch-out the graph of your journey to school

• Sketch means:

draw axes, use a ruler, make the graph the right shape but you don’t need numbers on the axes

Are You On Target Today?

Aims:-

4 describe a journey shown in a graph

5 explain how the graph shows the speed

6 link the graph to the formula for speed