Work and Power
5 marks · EasyA box of mass is lifted from the ground onto a platform high. It is then pushed horizontally for along the platform with a force of .
Calculate the work done to lift the box onto the platform.
Calculate the increase in gravitational potential energy (GPE) of the box after lifting.
Calculate the work done in moving the box horizontally on the platform.
Name the type of energy store that increases as the box is pushed along the platform.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 100 J
(b) 100 J
(c) 120 J
(d) Kinetic energy
Common mistakes: Uses mass instead of weight for work against gravity; Forgets to convert units
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly uses work = weight × height or mgh.
A1 (a) · 1 mark · Substitutes and calculates: 5 kg × 10 N/kg × 2 m = 100 J or equivalent.
B1 (b) · 1 mark · States GPE increase is same: 100 J. (follow-through)
A2 (c) · 1 mark · Calculates work for horizontal movement: 30 N × 4 m = 120 J.
B2 (d) · 1 mark · Identifies kinetic energy store as increasing.
Worked solution
a) Work done against gravity = m × g × h
b) The increase in GPE is equal to the work done: 100 J.
c) Work done = force × distance = 30 N × 4 m = 120 J.
d) The box's kinetic energy increases as it is moved.