4.5.2 Work Done and Energy Transfer

Question 1

What is meant by “work done” in physics?

Answer 1

Work is done when a force causes displacement of an object. It’s the transfer of energy from the force to the object as it moves through a distance.

Question 2

What is the equation for calculating work done?

Answer 2

WorkDone(W)=Force(F)×Distance(s)
Where:

�
W is in joules (J)

�
F is in newtons (N)

�
s is in metres (m)

Question 3

When can you use the work done equation?

Answer 3

Only when the force and the displacement are in the same direction. If the force is at an angle, use trigonometry or the component of force in the direction of motion.

Question 4

What is 1 joule of work equivalent to?

Answer 4

1 joule = Work done when 1 newton of force moves an object through 1 metre
So:

1
J
=
1

N
\cdotp
m
1J=1N\cdotpm

Question 5

What happens to energy when work is done?

Answer 5

Energy is transferred:

From the force doing the work

To the object being moved (usually as kinetic energy, heat, or elastic potential energy)

Question 6

What is the energy transfer when lifting an object vertically?

Answer 6

Work is done against gravity, so energy is transferred from the person’s muscles to the object’s gravitational potential energy store.

Question 7

What happens when work is done against friction?

Answer 7

Energy is transferred into thermal energy, causing a rise in temperature of the object and its surroundings. This energy is dissipated.

Question 8

A 10 N force moves an object 3 m. Calculate the work done.

Answer 8

W=F×s=10×3=30J

Question 9

Convert 50 newton-metres into joules.

Answer 9

Since
1

N
\cdotp
m
=
1
J
1N\cdotpm=1J,
50 N·m = 50 J

Question 10

Explain how understanding work done helps in real-life systems (e.g. engines or brakes).

Answer 10

It helps calculate how much energy is needed to move objects, and how much is lost as heat due to friction, which informs efficiency, safety, and design decisions.