Work, energy and power

Define work done

• product of force and distance moved

• product of force and displacement

• force x perpendicular distance from pivot

• ratio of force and distance moved in direction of force

What is the unit of work?

• N m^-1

• kg m s¯²

• kg m² s¯²

• kg m² s¯³

What is potential energy?

• energy stored due to height above the surface of Earth

• stored energy available to do work

• energy a body has due to its motion

• energy stored due to deformation

Distinguish between gravitational potential energy (GPE) and elastic potential energy (EPE).

I. GPE the energy stored due to height of object above the surface of Earth

II. EPE is due to deformation of object.

III. Both are stored energy available to do work

• I, II, III

• I and II

• I and III

• III only

• A

• B

• C

• D

• 404 μJ

• 404 mJ

• 404 J

• 404 kJ

• I, II

• II, III

• II, IV

• III, IV

Define power

• ratio of work done to time taken

• rate of doing work

• product of work and time

• product of force and velocity

• Wq

• Wr

• Wp + Wq

• Wp

A bungee jumper jumps from a platform and is decelerated by an elastic bungee cord, as shown.

At which part of the jump are all three types of energy non-zero?

• on the platform before the jump

• on the way down before the cord has started to extend

• on the way down as he decelerates

• at the bottom of the jump when the is stationary