A person is straining to lift a large crate, without success because it is too heavy. We denote the forces on the crate as follows: P is the upward force the person exerts on the crate, C is the vertical contact force exerted on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

P + C = W if in equilibrium?

P + C - W = 0; P + C = W

Explanation:

Action and reaction are equal and opposite according to newton's third law of motion. a force is that which tends to change a body's state of rest or uniform motion in a straight line, recall

P is the upward force the person exerts on the crate,

C is the vertical contact force exerted on the crate by the floor,

W is the weight of the crate

let the sum of upward forces be on the left hand side of the equation and the sum of downward forces on the right hand side.

P+C=W

P+C-W=0 if they are in equilibrium

the forces are related by the above.