# Another Question: Find the work done by the kinetic frictional force

1. Feb 25, 2005

### zizikaboo

A 300N force is pulling an 90.0 kg refrigerator across a horizontal surface. The force acts at an angle of 22.0° above the surface. The coefficient of kinetic friction is 0.200, and the refrigerator moves a distance of 6.00 m.

i found out the work done by pulling force is 1669 J and its asking for the work done by the kinetic frictional force!
here's what i did but the answer is wrong though...i tried a million times and it's still wrong! i know something's wrong here and i know it's not the acceleration of gravity or m...hmm

i did
mg times mu=9.8*90*.2
then i times it by the distance to get work. 176.4N*6m=1058.4 J
which is WRONG! arghh.......am i missing something here? :rofl:

2. Feb 26, 2005

### ehild

The friction is equal the normal force multiplied by the coefficient of friction.

$F_{fr} = \mu F_N$

As the refrigerator slides on a horizontal plane the vertical component of the resultant force is zero. This vertical component is the normal force + vertical component of the pulling force - mg.

$F_N+ F\sin (\alpha) - mg = 0$.

ehild