9th grade energy

Example

What is the kinetic energy of a 60 kg object moving at 5 m/s? Use Eₖ = ½ m v².

1. Eₖ = ½ × 60 × 5²
2. = 0.5 × 60 × 25 = 750
3. So the answer is: 750 J

Answer: 750 J

Example

A device is supplied with 200 J and transfers 30 J usefully. What is its efficiency, as a percentage?

1. 30 ÷ 200 × 100 = 15
2. So the answer is: 15%

Answer: 15 %

Example

A force of 20 N pushes a box 40 m along the floor. How much work is done, in J?

1. W = 20 × 40 = 800
2. So the answer is: 800 J

Answer: 800 J

Example

Is this energy resource renewable or non-renewable: nuclear fuel (uranium)?

1. Non-renewable resources will run out because they are not replaced.
2. So the answer is: non-renewable

Answer: non-renewable