Year 7 Science · Unit 3 · Lesson 10
Foundation Worksheet
Learning Goals
Match each machine to its description
Write the letter of the matching description in the middle column. Each letter is used once.
| Simple machine | Letter | Description and example |
|---|---|---|
| Lever | A. A sloped surface, such as a wheelchair ramp | |
| Wheel and axle | B. Two sloping surfaces joined to a thin edge, such as an axe head | |
| Pulley | C. A rigid bar that turns around a fulcrum, such as a crowbar | |
| Inclined plane | D. A grooved wheel with a rope running over it, such as on a flagpole | |
| Wedge | E. A sloping surface wrapped in a spiral, such as the thread on a jar lid | |
| Screw | F. A large wheel fixed to a smaller rod, such as a door handle |
True or false? Fix the false ones
Circle T or F. If a statement is false, correct it on the line.
1. A wedge, such as an axe head, is two inclined planes joined together.
Correct it:
2. On a seesaw, you can lift a heavier friend if you sit further from the middle than they do.
Correct it:
3. A lever creates extra energy, which is why it makes lifting easier.
Correct it:
4. A fixed pulley bolted to a ceiling beam halves the force you need to lift a load.
Correct it:
5. A movable pulley reduces the force you need, but you must pull the rope about twice as far.
Correct it:
Sort the levers
Ask “Which part is in the middle?” Fulcrum in the middle: Class 1. Load in the middle: Class 2. Effort in the middle: Class 3. Write each lever in the correct box. The boxes do not hold the same number of items.
Class 1
Class 2
Class 3
1. A wheelbarrow is a lever. Say where the fulcrum, the load and the effort are on a wheelbarrow, and name its class.
Read the data: the stage crew
Scenario: raising a sandbag
The school drama crew must raise a 120 N sandbag 1 m to the top of the stage frame. They try four set-ups. They measure the effort with a spring scale and how far they pull.
| Set-up | Effort force (N) | Distance pulled (m) |
|---|---|---|
| Lifting straight up by hand | 120 | 1 |
| One fixed pulley | 126 | 1 |
| One movable pulley | 64 | 2 |
| Block and tackle (4 rope segments hold the bag) | 34 | 4 |
Source: sample class results.
2. Which set-up needed the smallest effort? Use Table 1 to say what the crew had to do in exchange.
3. Calculate the mechanical advantage of the movable pulley. Use MA = output force (120 N) ÷ input force.
MA = (no unit)
4. Jai says: “The fixed pulley was useless: it did not reduce the effort.” Explain what a fixed pulley does do, and suggest why its effort was over 120 N.
5. Ruby uses a crowbar resting on a small stone to lift a boulder she cannot lift by hand. She says: “The crowbar gave me extra energy.” Explain how the crowbar works and whether Ruby is right.
Match each machine to its description
Lever → C; Wheel and axle → F; Pulley → D; Inclined plane → A; Wedge → B; Screw → E.
True or false
1. True. 2. True. 3. False: no machine creates energy; a lever trades a smaller force for a longer distance. 4. False: a fixed pulley only changes the direction of the force (MA = 1). 5. True.
Sort the levers
Class 1: a seesaw; a crowbar; pliers; scissors. Class 2: a bottle opener; a garlic press; a nutcracker. Class 3: tweezers; a fishing rod.
Question 1
Fulcrum: the wheel at the front (1). Load: the contents of the tray (1). Effort: your hands lifting the handles; the load is in the middle, so it is a Class 2 lever (1). [3 marks]
Read the data: the stage crew
2. The block and tackle, 34 N (1). In exchange they had to pull the rope 4 m to raise the bag 1 m, four times as far (1). [2 marks]
3. MA = 120 ÷ 64 (1) = 1.9, about 2 (1). [2 marks]
4. A fixed pulley changes the direction of the force, so the crew can pull down instead of lifting up (1). Its MA is about 1, so it is not meant to reduce the effort; pulling down is easier, using body weight (1). The extra 6 N is used to overcome friction in the pulley wheel and rope (1). [3 marks]
Question 5
Marking guide: 1 clear position (Ruby is wrong); 1 parts named: fulcrum = the small stone, load = the boulder, effort = Ruby’s push on the far end, so it is a Class 1 lever; 1 the fulcrum is close to the load, so the mechanical advantage is greater than 1 and a small effort force lifts a large load; 1 trade-off: Ruby’s end moves a long distance while the boulder rises only a little; 1 no energy is created: it saves force, not energy. [5 marks]
Model answer: Ruby is wrong. The crowbar is a Class 1 lever: the small stone is the fulcrum, the boulder is the load and Ruby’s push on the far end is the effort. The fulcrum is close to the boulder, so the MA is greater than 1 and a small force lifts a large load. The catch is distance: her end moves a long way while the boulder rises only a little. The crowbar saves force, not energy.
Common error: “a fixed pulley halves the force.” It only changes the force’s direction.