Physics question below

Question

 

You slide a block with a mass of m down an incline plane with a height of h that has a length of L. If there is a kinetic friction f acting on the object as it slides down the incline then at the bottom of the hill it will have a kinetic energy of...

 

a

mgh - fL

b
mgL

c
mgh
d
gL

e
ghL - fm

f
mgh - fh

g
mgL - fh

h
fh - mg

i
ughhhhhhhhhhhh

j
mgL - fL

Answer 1

You slide a block with a mass of m down an incline plane with a height of h that has a length of L. If there is a kinetic friction f acting on the object as it slides down the incline then at the bottom of the hill it will have a kinetic energy of...

 

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I assume, "f" is the kinetic friction force. If so, then this force performs fL work durng complete descent.

This means, body's potential energy mgh has spent some its portion, exactly fL, so that eventually

effective potential energy( which will transfer to kinetic energy at the bottom) has been reduced to mgh-fl.

 

Now, consider two cases:

1) no friction.

 

the kinetic energy at the ground level would be  mgh

 

Thus, your answer is choice a)  mgh-fL

 

 

2) with given kinetic friction

 

 

kinetic energy would be  mgh-fL