Polly is pushing a box across the floor with a force of 30 n. the force of gravity is –8 n, and the normal force is 8 n. which value could describe the force of friction if polly could not move the box?
–30 n
–8 n
8 n
30 n

Frictional force f = -30 N

Explanation:

It is given that, Polly is pushing a box across the floor with a force of 30 N. The other forces that are acting on the box are :

1. Force of gravity = -8 N

2. Normal force = 8 N

The above two forces are acting on the box such that there is no motion in the box in vertical direction.

We know that frictional force is an opposing force. It always act in the opposite to the direction of motion.

From the third law of Newton, it is clear that there is always an equal and opposite force in the direction opposite to the direction of motion.

Here, applied force is 30 N. So, the frictional force must be (-30 N). Hence, the correct option is (a) "-30 N".

A

Explanation: