Crane Lifting a Car -- Find the Work Done

[stphnls]

Homework Statement

A car of mass 2000kg is loaded by a crane exerting an upward force of 30kN. With
this constant force, the car moved 4m. Find the a.) work done by the crane b.) work
done by the gravity c.) the speed of the car after 4m.

Relevant Equations

W(total)=1/2m2v2^2-1/2m1v1^2
Work=Fd
Work=Fdcos theta

W= Fd
W= 3NX1.20m
W= 3.6 J is the work done by the crane
W=Fd
W=0.6Nx1.20m
W=0.72 J is the work done by the car
I have no idea how to solve the c, I am thinking at first that the work done by the crane and the car are zero because cos 90 is zero and there are perpendicular to each other. I really don't know what to do.

 

[kuruman]

Welcome to PF @stphnls

W=0.72 J is the work done by the car

Work done by the car on what? Where did you get the numbers 0.6 N and 1.20 m?

Use the work-kinetic energy theorem. You have to assume that the car starts from rest because no information is given to the contrary. Also note that the crane exerts a force of 30 kN = 30,000 N.