Question

Person X and Y are pushing a block against each other and the block does not move. This is because the net force is .

• A. zero
• B. negative
• C. positive

Answer 1

The correct option is A zero

A net force is the vector sum of forces acting on a body. Assuming that two forces are acting on a body, consider the following cases,
Case 1:
If they act in the same direction, the forces are added up, $F=F_1+F_2$
Case 2:
If they act in the opposite directions, they try to cancel out each other and the net force is the differences between the forces and the object moves in the direction of the greatest force applied, $F=F_1-F_2$

In the above mentioned example, the block does not move when the forces applied are opposite to each other. This implies that the forces applied by X and Y cancels each other exactly or Force of X = Force of Y, making the net force applied on the object to be zero.