Question

A man pulls a sled at a constant velocity across a horizontal snow surface. if a force of 80 lb is being applied to the sled rope at an angle of 53˚ to the ground, what is the force of friction between sled and snow

Answer 1

For the above situation we will draw a force diagram first

Now as per force diagram we can see that there is a component of force parallel to the surface due to which sled is pulled forward.

Now this force must be counter balanced by friction force as the sled is moving with constant speed.

So if sled is moving with constant speed it will have net force ZERO

by Newton's II law

`F_(net) = ma= 0`

so we can say

`F_(friction) = Fcos\theta`

`F_(friction) =80cos53`

`F_(friction) = 48 lb`

So friction force on it is 48 lb.