Mistake in solving for work in physics?

[princesspriya]

Homework Statement

a student wearing a frictionless in-line skates on a horizontal surface is pushed by a friend with a constant force of 45N. How far must the student be pushed, starting from rest, so that her final kinetic energy is 352J?

Homework Equations

The Attempt at a Solution

KE=1/2MV^2
352=1/2*(45/9.81)*V^2
Vf=12.39 and Vi=0 since it starts from rest

Wnet=1/2MVf^2-1/2MVi^2
1/2*(45/9.81)*12.39^2=352.31

Wnet=FnetDCosX
352.31=45dcos0
d=7.83m

I just wanted to know if that was a correct way of solving it or did i make a mistake somewhere?
thx for the help.

 

[Doc Al]

The Attempt at a Solution

KE=1/2MV^2
352=1/2*(45/9.81)*V^2
Vf=12.39 and Vi=0 since it starts from rest

Wnet=1/2MVf^2-1/2MVi^2
1/2*(45/9.81)*12.39^2=352.31

Since you are given the final KE, these calculations are not needed. (Note how error creeps in: 352.31 should really be 352.)

Wnet=FnetDCosX
352.31=45dcos0
d=7.83m

This is all you need. (Use the given value for KE.)

 

[princesspriya]

the Wnet is always the same as KE?

 

[Doc Al]

the Wnet is always the same as KE?

The net work will equal the change in KE. That's the so-called Work-KE theorem.

 

[princesspriya]

ooo thxx hehe