Question

In a shipping yard, a crane operator attaches a cable to a 1240-kg shipping container and then uses the crane to lift the container vertically at a constant velocity for a distance of 37 m. Determine the amount of work done by each of the following.

(a) the tension in the cable
(b) the force of gravity

Answer 1

Answer:

a) $W_T=449624\ J$

b) $W_g=-449624\ J$

Explanation:

Given:

mass of the container, $m=1240\ kg$

displacement of the container, $h=37\ m$

Since the load is lifted using cable there will be weight acing downwards and the tension in the cable will act upward which will be equal in magnitude to the weight.

So,

$T=m.g$ (upwards)

$T=1240\times 9.8$

$T=12152\ N$

Now the work done by the tension:

$W_T=T\times h$

$W_T=12152\times 37$

$W_T=449624\ J$

Now the work done by the gravity:

$W_g=m.g.(-h)$ since displacement is in opposite direction to the gravity

$W_g=1240\times 9.8\times (-37)$

$W_g=-449624\ J$