Question

You are pushing a sled in which your little sister is seated up a 21° slope (one that makes an angle of 21° with the horizontal). If the mass of the sled and girl is 47 kg, and the coefficient of kinetic friction between the sled and the surface is 0.100, with what magnitude of force do you need to push in order for the sled to move with constant velocity?

Answer 1

Answer:

The answer is: 212.3112

Explanation:

-First we need to know that if we want to push in order for the sled to move with constant velocity so there is no acceleration and hence the sum of forces is equal to 0.

-Second we need to know:

Friction force  = Normal Force x kinetic friction

Normal force = Weight x cos(21°)

-Third:

$F - F_{fr} - Wsin(21^{o} ) = 0 \\F_{fr} = N*u_{r} = W*cos( 21^{o})*0.1=47*10*cos( 21^{o})*0.1\\F_{fr} = 43.8782$

Finally:

$F - 43.8782 - 47*10*sin(21^{o} ) = 0\\F = 212.3112$