A gardener of mass is standing on a small trolley of mass that can move without…
PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A gardener of mass 60kg is standing on a small trolley of mass 20kg that can move without friction on a horizontal track. The system is initially at rest relative to the ground.
(i) The gardener throws a 2kg bag of fertiliser horizontally forward with a speed of 5ms−1 relative to the ground. Calculate the velocity of the trolley–gardener system immediately after the throw.
(ii) Just after the throw, a weak horizontal friction force of magnitude 8N starts acting opposite to the direction of motion of the trolley. Assuming the force remains constant for 2s, determine the final velocity of the trolley–gardener system at the end of this interval.
(iii) Justify in one or two sentences whether the momentum of the gardener–trolley–bag ensemble is conserved during (a) the instant of throw and (b) the subsequent 2s interval.