a) How much work is done in lifting a 1.2-kg book off the floor to put it on a desk that is 0.5 m high? Use the fact that the acceleration due to gravity is g = 9.8 m/s2. (b) How much work is done in lifting a 19-lb weight 8 ft off the ground?

a) 5.88Nm b) 206.30Nm

Explanation:

Work is said to be done when a force applied to an object causes the object to change its position.

Mathematically, work done = Force * Distance

Given distance = height = 0.5m

Force = weight of the object = mass * acceleration due to gravity

Weight = 1.2*9.8

Weight = 11.76N

Work done = 11.76 * 0.5

Work done = 5.88Nm

b) Using similar formula as in question a;

Work done = Force * Distance

Given weight = 19lb

Since 1lb = 4.45N

19lb weight = 19*4.45 = 84.55N

Distance of object from the ground = 8ft

Since 1ft = 0.305m

8ft = 0.305*8 = 2.44m

Work done = 84.55*2.44

Work done = 206.30Nm