Year 7 Science · Unit 3 · Lesson 6
Extension · Foundation Worksheet
Learning Goals
Extension · optional
Newton's Second Law sits in Stage 5 (SC5-WAM-01), beyond the Stage 4 Forces dot points this unit is built on. Nothing on this sheet is assessed as part of Year 7 Forces, so it is enrichment rather than required practice. Do it if you are interested, and skip it without losing any marks if you are not.
Fill the gap
Choose the correct word from the word bank. Each word is used at most once. Two words are not needed: cross them out.
Newton's Second Law links three things: the on an object, its , and the that results. When the same push is given to a lighter object, it speeds up more quickly. An object always accelerates in the same as the force on it. The law is named after Isaac .
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. When the same force is applied, more mass means more acceleration.
Correct it:
2. If you double the force on an object and keep its mass the same, its acceleration doubles.
Correct it:
3. A tennis ball and a shot put thrown with the same force accelerate at the same rate.
Correct it:
4. A heavy object pushed very hard can accelerate more than a light object pushed gently.
Correct it:
5. A waterlogged football kicked with the same force as a dry football accelerates less.
Correct it:
Which accelerates more?
For each pair, write A, B or Same.
| Object A | Object B | A, B or Same? |
|---|---|---|
| An empty wheelbarrow pushed with 30 N | The same wheelbarrow full of soil, pushed with 30 N | |
| A go-kart pushed with 50 N | The same go-kart pushed with 100 N | |
| A 1 kg cart pushed with 10 N | A 2 kg cart pushed with 20 N | |
| A cricket ball hit by a bat | A bowling ball hit with the same force |
1. At the Bathurst 1000 car race, teams work hard to make their cars lighter. The engine gives about the same driving force either way. Explain why a lighter car is quicker to speed up out of a corner.
Read the data
Scenario: pulling a trolley
A class pulls the same trolley along a smooth bench with a spring balance, keeping the pulling force steady. They time how long the trolley takes to travel 2 m from a standing start.
| Pulling force (N) | Time to travel 2 m (s) |
|---|---|
| 2 | 2.0 |
| 4 | 1.4 |
| 6 | 1.2 |
| 8 | 1.0 |
Source: sample class results.
2. What happens to the time as the pulling force gets bigger? What does this tell you about the trolley’s acceleration?
3. The class then loads two bricks onto the trolley and pulls with 8 N again. Predict whether the time will be more or less than 1.0 s, and explain.
4. Would you rather push a shopping trolley full of bricks or one full of feathers? Explain using force, mass and acceleration. Then describe what you would have to do to make the brick trolley speed up as quickly as the feather trolley.
Fill the gap
force; mass; acceleration; direction; net; Newton. Not used: gravity, speed. Six correct = 3; four or five = 2; two or three = 1. [3 marks]
True or false
1. False: for the same force, more mass means less acceleration. 2. True. 3. False: the tennis ball has far less mass, so it accelerates far more. 4. True. 5. True.
Which accelerates more?
1 each: A (less mass, same force); B (more force, same mass); Same (double the force on double the mass); A (much less mass). [4 marks]
Question 1
The force stays about the same, so mass is what changes (1). For the same force, less mass gives more acceleration, so the lighter car speeds up faster (1). [2 marks]
Read the data: Question 2
The time gets shorter, from 2.0 s to 1.0 s (1). The trolley speeds up more quickly: a bigger force gives a bigger acceleration (1). [2 marks]
Question 3
More than 1.0 s (1): the bricks add mass, and the same force on more mass gives less acceleration (1). [2 marks]
Question 4
Marking guide: 1 chooses feathers; 1 the brick trolley has much more mass; 1 the same push on more mass gives less acceleration; 1 push the brick trolley much harder (a bigger force); 1 uses force, mass and acceleration correctly. [5 marks]
Model answer: The feather trolley. It has much less mass, so the same force gives it more acceleration. The brick trolley has more mass, so my push speeds it up only slowly. To make it accelerate as quickly, I would need a much bigger force.
Common error: saying a bigger force makes something “faster”; force gives acceleration, a change in speed.