What is the scientific definition of work?

Any physical or mental effort that makes you tired A force acting on an object and causing it to move a distance in the direction of that force The energy stored inside an object due to its position The rate at which energy is transferred per second

You carry a heavy suitcase horizontally along a flat airport corridor without lifting or lowering it. Is the upward force you exert on the suitcase doing any work on it?

Yes — you are clearly putting in effort, so work must be done Yes — the suitcase is moving, so any force acting on it must do work No — the force you exert is upward but the suitcase moves horizontally, so the force and displacement are at right angles and no work is done by that force No — you would have to be running for work to be done

You push against a solid brick wall as hard as you can for five minutes. The wall does not move. How much work have you done on the wall?

A large amount — you exerted a large force for a long time A small amount — some energy must have been transferred to the wall through vibration Zero — work requires displacement; since the wall did not move, no work was done on it It depends on how hard you push — harder force means more work

What is the SI unit of work?

The watt (W) The newton (N) The joule (J) — the same unit used for energy The kilogram-metre (kg·m)

A force of 10 newtons moves a box 5 metres along the floor in the direction of the force. How much work is done on the box?

2 joules 15 joules 50 joules 500 joules

What is 'negative work'?

Work that is calculated incorrectly and gives a negative number by mistake Work done by a force that acts opposite to the direction of motion, removing kinetic energy from the object Work done in a downward direction, such as when a crane lowers a load Work done below the surface of the ground

You throw a ball straight upward. During the upward journey, what kind of work is gravity doing on the ball?

Positive work — gravity always adds energy to moving objects Zero work — gravity only acts horizontally Negative work — gravity acts downward but the ball moves upward, so gravity opposes the motion and removes kinetic energy No work — gravity does not act on thrown objects

Which of these is an example where NO scientific work is being done?

A horse pulling a cart along a road A crane lifting steel beams A student holds a 10 kg textbook at arm's length without moving for two minutes A football rolling across a grass field and slowing down

The work-energy theorem states that the net work done on an object equals:

The object's total potential energy The change in the object's kinetic energy The force applied to the object multiplied by its mass The object's speed at the end of the motion

Ball A is pushed 2 metres by a 5 N force. Ball B, identical to A, is pushed 4 metres by the same 5 N force. How does the work done on Ball B compare to the work done on Ball A?

The same — same force means same work regardless of distance Half as much — the force is spread over a longer distance Twice as much work is done on Ball B — doubling the distance doubles the work when force is constant Four times as much — both distance and time are different