Work, Energy and Power

A force of 20 N moves an object 5 m in the direction of the force. How much work is done?

1. 25 J
2. 0.25 J
3. 4 J
4. 100 J

What is the kinetic energy of a 2 kg mass moving at 3 m/s?

1. 3 J
2. 18 J
3. 6 J
4. 9 J

A 5 kg mass is raised 4 m. How much gravitational potential energy does it gain? (g = 10 m/s²)

1. 20 J
2. 50 J
3. 9 J
4. 200 J

600 J of work is done in 30 s. What is the power?

1. 20 W
2. 570 W
3. 18,000 W
4. 630 W

How many joules are there in 1 kWh?

1. 3.6 × 10³ J
2. 3600 J
3. 3.6 × 10⁶ J
4. 1000 J

A machine gives out 400 J of useful energy for every 500 J put in. What is its efficiency?

1. 90%
2. 20%
3. 80%
4. 125%

A ball is dropped from 5 m. Ignoring air resistance, how fast is it moving just before it lands? (g = 10 m/s²)

1. 100 m/s
2. 10 m/s
3. 5 m/s
4. 50 m/s