Answer: 296.1 J or 6.98 kJ
Explanation:
Given
Length of chain, l = 11 m
Mass of chain, m = 95 kg
It is worthy of note that chain has two ends. So this depends which of the two ends should end up at
the given height of 7 m.
Scenario 1. If it is the leading end:
Weight of chain raised
W = mg/l
W = 9.8×95/11
W = 84.6 N
Height raised = ½ m (which is the height of the centre of gravity of the raised portion).
Work done = 84.6 × 1/2 * 7 = 296.1 Joules
Scenario 2. If it is the trailing end:
Weight of chain raised = 9.8×95 = 931 N.
Height raised (average) = 12.5 m (5.5 m for the chain midpoint + 7 m off the ground)
Work done = 931 × 7.5 = 6.98 kJoules
Thus, the work required is either of 296.1 J or 6.98 kJ
