Question

A mover pushes a 20 kg crate across a level floor with a force of 200 N, but the crate accelerates at a rate of only 7.5 m/s2 because a friction force opposes the crate's motion. What is the magnitude of this force of friction?Force of FrictionA. 50 NB.100 NC. 15 ND. 25 N

Answer 1

`A\text{.}50N`

Step-by-step explanation

Parameters given:

Mass of crate, m = 20 kg

Force of push, F = 200 N

Acceleration of crate, a = 7.5 m/s²

To find the force of friction, we have to apply the net force acting on a body. The sum of all forces acting on the crate is equal to the product of its mass and its acceleration.

Therefore, we have:

`F_{\text{net}}=F-F_f`

where Ff = force of friction

Therefore, we have that:

`\begin{gathered} m\cdot a=200-F_f \\ 20\cdot7.5=200-F_f \\ 150=200-F_f \\ \Rightarrow F_f=200-150 \\ F_f=50N \end{gathered}`

That is the force of friction. (Option A)