Topic 6: Forces and Energy (PAPER TWO)

Question 1

When is work done?

Answer 1

When a force moves an object through a distance, work is done on the object and energy is transferred

Question 2

What happens when you push something along a rough surface?

Answer 2

When you push something along a rough surface, you are doing work against frictional forces. Energy is being transferred to thermal energy stores due to friction. This then causes the overall temperature of the object to increase.

Question 3

What is power?

Answer 3

Power is the rate of energy transfer (or how much work is done per second)

Question 4

What does it mean if an object is in equilibrium?

Answer 4

The forces on it are balanced

Question 5

How can you calculate the resultant force (vector diagram)

Answer 5

Parallelogram + line from corner to corner

Question 6

What’s a moment?

Answer 6

A moment is the turning effect of a force

Question 7

What’s the equation for a moment?

Answer 7

Moment (Nm) = Force (N) x distance normal to the direction of the force (m)

Question 8

A good javelin thrower will try to extend their arm as much as possible before releasing the javelin.
Explain why this allows them to do more work on the javelin

Answer 8

Work done = force x distance
So, if their arm is extended it can move further and they can push the javelin forward for longer