Question

a 4.0 kg object is acted upon by a 20 n force to the right and a 25 n force to the left. what is the magnitude of the objects accerlation

Answer 1

Netwon's second law states that the resultant of the forces acting on an object is equal to the product between the object mass and its acceleration:
$\sum F = ma$

In this problem, the resultant of the forces is
$\sum F = 25 N - 20 N = 5 N$ (to the left)
so if we use the previous equation, we find the acceleration of the object:
$a= \frac{\sum F}{m}= \frac{5 N}{4.0 kg}=1.25 m/s^2$
and the acceleration is to the left, since the resultant of the forces is to the left.