Answer & Explanation
First of all, we need to find the force of the cable.
Noting that the friction force always working in the opposite direction of the motion of the object.
We know, from Newton's second law, that
And we know that
We know that the work done by some force is given by
so the work done by the cable force on the car during this process is given by
Plug from (1), and noting that cos
Now plug the given;
The work done by the gravitational force is given by
Noting that \theta= 180° since the angle between the gravitational force and the velocity is
Noting that cos
Plug the given;
The total work done on the lift is the work done by the net force exerted on the car during this process.
We know that the net force exerted on the car during this process is zero since the car is moving at a constant speed (see part a above).
mass of elevator m=1500 kg
Lifting height =40 m
Friction Force F=100 N
The cable has to work against gravitational force and friction Force
Increase in Potential Energy of Elevator =mgh=1500
thus work done by gravitational force = 588 kJ
Work done against friction force = F * x =100 * 40=4 kJ
Total Work done by the cable = 592 kJ
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