Finding Change in Kinetic Energy

[student54321]

Homework Statement

A mass of 8.50 kg is traveling 7.50 m/s
[up]. It is acted on by a force of 340 N [up]
over a displacement of 15.0 m [up].

What is the change in kinetic energy

Homework Equations

Ek = 1/2mvsquared. F = mv. w = fd

The Attempt at a Solution

I tried doing the equation Ek = 1/2mvsquared, and was off by 3000 or so.

 

[cepheid]

Homework Statement

A mass of 8.50 kg is traveling 7.50 m/s
[up]. It is acted on by a force of 340 N [up]
over a displacement of 15.0 m [up].

What is the change in kinetic energy

Homework Equations

Ek = 1/2mvsquared. F = mv. w = fd

The Attempt at a Solution

I tried doing the equation Ek = 1/2mvsquared, and was off by 3000 or so.

That's because you probably used the INITIAL speed. The speed will change, because there is a force acting on the object.

1. Figure out the work done on the object (don't forget to consider all forces acting on it).

2. Use the work-energy theorem to figure out the object's change in kinetic energy given the work done in part 1.