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Mistake in solving for work in physics?

1. 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?


2. Homework Equations



3. 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.
 

Answers and Replies

Doc Al
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1,083
3. 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.)
 
the Wnet is always the same as KE?
 
Doc Al
Mentor
44,827
1,083
ooo thxx hehe
 

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