Question

An object has a mass of 15 kg and is accelerating to the right at 16.3 m/s2. The free-body diagram shows the horizontal forces acting on the object.

A free body diagram with 2 forces. The first vector is pointing right, labeled F Subscript a Baseline 250 N. The second vector is shorter pointing left, labeled F Subscript f Baseline.
What is the frictional force, Ff, acting on the object?

-5.5 N
-15 N
-244.5 N
-494.5 N

Answer 1

Take right as positive. Newton's 2nd law: ΣF = ma.

250 N + Ff = (15 kg)(16.3 m/s^2) = 244.5 N

So Ff = 244.5 − 250 = −5.5 N.

The frictional force is −5.5 N (5.5 N to the left).