<h2>
Answer:</h2>
(a) 1.629 kJ
(b) 0.132 kW
<h2>
Explanation:</h2>
The workdone (W) on a body is the product of the force (F) acting on the body and the displacement (s) caused by the force. This can be written as;
W = F x s ----------------(i)
Where;
F = m x a [From Newton's law] ------------------(ii)
m = mass of the body
a = acceleration of the body
Since the direction of motion is upwards, the acceleration acting on the body is the one due to gravity.
i.e a = g = 10m/s²
From the question, the mass of the crate is 90.5kg.
Substitute these values into equation (ii) to get the force acting on the body as follows;
F = 90.5 x 10
F = 905N
From the question;
The displacement (s) of the crate is 1.80m
Substitute the values of the force F and the displacement s into equation (i) as follows;
W = 905 x 1.8
W = 1629 J
Convert the result to kJ by dividing by 1000 as follows;
W = (1629/1000) kJ
W = 1.629 kJ
Therefore, the work done on the crate is 1.629 kJ
(b) Power (P) is the ratio of work done (W) to the time taken (t) to do the work. i.e;
P = W / t -----------------(ii)
From the question;
t = 12.3s
Also;
W = 1.629 kJ [as calculated in a]
Substitute these values into equation(ii) as follows;
P = 1.629 / 12.3
P = 0.132 kW
Therefore the useful power supplied to the crate is 0.132 kW
