Question

The sliding frictional force between 4 kg box and the floor is 15 N. It is pushed across the floor with a constant force such that it accelerates at $0.8m{s}^{-2}$. What is the force applied to the box?

• A. 16.6 N
• B. 18.2 N
• C. 20 N
• D. Zero

Answer 1

The correct option is B 18.2 N

Mass of the block $=m=$ 4kg
Acceleration $a=0.8m/s^2$
Therefore, net force acting on the block *in the direction of motion $=F=ma=3.2N$
This force is achieved after overcoming the opposing frictional force of 15N(f)
Therefore, the total force to be applied
F' $=F+f=15+3.2=$ 18.2 N
hence the force applied to the box is 18.2N.