Work & Energy Flashcards

All 6 cards in this deck

What is the equation for work done?

work done (J) = force (N) × distance moved in the direction of the force (m)

What is the relationship between energy transferred and work done?

They are equal: energy transferred (J) = work done (J).

What is 1 joule written in newton metres?

$1\text{ J} = 1\text{ N m}$ — one joule of work is done when a force of 1 N moves an object 1 m in the direction of the force.

What are the steps to find the force from the work done and the distance moved?

e.g. a cyclist does 1600 J of useful work travelling 28 m

1. Write the equation: work done = force × distance, so $1600 = F \times 28$
2. Rearrange: $F = 1600 \div 28$
3. Force = 57 N

What are the steps to measure the work done by a force in the laboratory?

e.g. pulling a wooden block along a bench

1. Measure the pulling force with a newtonmeter: e.g. 5 N
2. Measure the distance moved in the direction of the force with a ruler: e.g. 2 m
3. Multiply: work done = $5 \times 2 = 10$ J

True or false? A porter carrying a suitcase horizontally at a steady height does work against gravity.

False. The upward force is at right angles to the motion, so no distance is moved in the direction of the force and the work done is zero.