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Simple Machines: Levers, Pulleys and Ramps — Answers

Answer sheet with model answers and success criteria for the Year 6 forces & motion worksheet.

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Success TutoringWorksheetsAnswer sheetYear 6 · Science · Forces & Motion

Simple Machines: Levers, Pulleys and Ramps — Answers

Part A: The six simple machines

Read the passage, then answer the questions.

A simple machine is a device that makes a job easier by changing the size or the direction of a force. There are six simple machines: the lever, pulley, inclined plane (ramp), wheel and axle, wedge and screw.

A lever is a rigid bar that turns around a fixed point called the fulcrum (or pivot). The force you apply is the effort, and the object being moved is the load.

A pulley is a wheel with a rope around it. A fixed pulley changes the direction of the force. A movable pulley, attached to the load, halves the force needed.

1.Match each simple machine to an everyday example.
  • lever
  • pulley
  • inclined plane
  • wheel and axle
  • wedge
  • screw
  • a flagpole rope that raises a flag
  • an axe blade
  • a door knob
  • a seesaw
  • a jar lid
  • a wheelchair ramp

Answer: lever → a seesaw; pulley → a flagpole rope that raises a flag; inclined plane → a wheelchair ramp; wheel and axle → a door knob; wedge → an axe blade; screw → a jar lid

2.The fixed point that a lever turns around is called the (answer space).

Answer: fulcrum

Also accept: pivot.

3.In a wheelbarrow, where is the fulcrum?
  1. Athe handles
  2. Bthe wheel
  3. Cthe load in the tray
  4. Dthe person's hands

Answer: the wheel

The wheelbarrow turns around its wheel. The load is in the tray and the effort is applied at the handles.

4.What does a single fixed pulley (like the one at the top of a flagpole) do?
  1. Ahalves the force needed
  2. Bchanges the direction of the force, so you pull down to lift up
  3. Cmakes the load lighter
  4. Dremoves friction

Answer: changes the direction of the force, so you pull down to lift up

A single fixed pulley does not reduce the force, but pulling down is often easier than lifting up.

Part B: Calculating with simple machines

Show your working.

Balancing a lever: a lever balances when force × distance from the fulcrum is the same on both sides. A smaller force can balance a bigger one if it is further from the fulcrum.

Ramps: if we ignore friction, force × distance is the same whether you lift a load straight up or push it up a ramp. A longer ramp means less force, but more distance.

5.Mia weighs 400 N and sits 1.5 m from the middle of a seesaw. Her brother weighs 300 N. How far from the middle must he sit, on the other side, to balance the seesaw?

Answer: 2 m

  1. 400 × 1.5 = 600
  2. 600 ÷ 300 = 2 m
6.Ignoring friction, lifting a 600 N box straight up 1 m needs a force of 600 N. How much force is needed to push it up a 3 m long ramp to the same height?

Answer: 200 N

  1. force × distance stays the same: 600 × 1 = 600
  2. 600 ÷ 3 = 200 N
7.A 400 N load hangs from a single movable pulley. Ignoring friction and the weight of the pulley, how much force is needed to lift it?

Answer: 200 N

  1. A movable pulley halves the force.
  2. 400 ÷ 2 = 200 N
8.Using the ramp, what do you have to do in exchange for using less force?
  1. Apush the box a longer distance
  2. Blift the box higher
  3. Cpush the box faster
  4. Duse a heavier box

Answer: push the box a longer distance

Simple machines trade force for distance: less force, but over a longer distance.

Part C: True or false?

Write True or False.

9.Simple machines reduce the total amount of work (energy) needed to do a job.

Answer: False

They make a job easier by reducing the force, but you must apply it over a longer distance, so the energy needed is not reduced (and friction adds a little more).

10.A longer spanner (wrench) makes it easier to turn a tight nut.

Answer: True

Applying the effort further from the pivot gives more turning effect for the same force.

11.A door is easier to push open near its hinges than near its handle.

Answer: False

The hinges are the pivot. Pushing far from the pivot, near the handle, gives a bigger turning effect, so the door is easier to open there.

12.A screw is like an inclined plane wrapped around a rod.

Answer: True

The thread of a screw is a long ramp wound around a cylinder.

13.A pair of scissors is made from two levers.

Answer: True

Each blade is a lever, and the screw joining them is the fulcrum.

Part D: Explain it

14.A builder needs to move a heavy barrel onto the back of a truck. Compare using a ramp with using a pulley system. For each, explain how it makes the job easier and what the builder has to give up in exchange.

Model answer: A ramp lets the builder roll or push the barrel up a gentle slope instead of lifting it straight up. It needs much less force, but the builder must move the barrel a longer distance along the ramp. A pulley system with a movable pulley halves the force needed and lets the builder pull down on a rope, which is easier than lifting. In exchange, the builder has to pull twice as much rope as the height the barrel rises. Both machines trade a smaller force for a longer distance.

Success criteria:

  • Explains how the ramp reduces force
  • Explains how the pulley reduces force or changes direction
  • Identifies the trade-off of greater distance for each
  • Uses correct terms (force, load, effort, distance)
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