Calculating work done by a force?

[chrismeng]

Homework Statement

An object initially at an elevation of 5 m relative to the Earth's surface with a velocity of 50 m/s is acted on by an applied force R and moves along a path. Its final elevation is 20 m and its velocity is 100 m/s. The acceleration of gravity is 9.81 m/s^2. Determine the work done on the object by the applied force, in kJ.

Homework Equations

Work of all non-gravity forces = Change in KE + Change in PE

The Attempt at a Solution

I can get the work done by R in terms of the mass using the equation
Work of all non-gravity forces = Change in KE + Change in PE
but the problem doesn't tell us the mass and I don't know what other equation to use to set up a system of equations to eliminate the mass.

 

[TSny]

Welcome to PF!

You are right. Without the mass, you cannot find a numerical value for the work done by the applied force.

 

[chrismeng]

Welcome to PF!

You are right. Without the mass, you cannot find a numerical value for the work done by the applied force.

I thought so! thanks for the help

 

[Austin Hook]

I get the impression that the conclusion is that the question is invalid. Not necessarily so however. Since the result is dependent on the unknown mass, it likely should be presumed that the question is simply asking for a formula as an answer, with the mass as a parameter in it. One would also have to specify the units of the mass in such an answer since the question is so specific in asking that the work deduced is explicitly in kj.