Answers to AQA GCSE Gears

Practice questions

1.What are gears used for?

A gear is used to change the moment of a turning effect. So, they can multiply the turning effect to increase or decrease it.

2. The teeth of one gear cog will exert a 10N downward force on a 2nd gear cog. State the size and direction of the force that the 2nd gear cog will exert on the first gear cog

Where the teeth of the gear cogs meet the gear cogs will exert equal and  opposite forces on each other.

So, in this case the 2nd gear cog will exert a 10N upward force.

3. A small gear cog has a radius of 5cm and a 2nd gear cog has a radius of 20cm. If the smaller gear cog rotates 50 times per minute, calculate the number of rotations per minute that the large cog completes.

The larger gear cog is 4 times bigger than the first gear cog, so it rotates 4 times slower. Therefore 50/4 = 12.5 times per minute.