Question

numerical of newton's first law of motion -class9​

Answer 1

1. A person is in an elevator that moving upward at a constant velocity. The weight of the person is 800 N. Immediately the elevator rope is broke, so the elevator falls. Determine the normal force acted by elevator’s floor to the person just before and after the elevator’s rope broke.

A. 800 N and 0

B. 800 N and 800 N

C. 1600 N and 0

D. 1600 N and 800 N

Known :

Weight (w) = 800 Newton

Wanted: The normal force (N)

Solution :

Before the elevator’s rope broke

When the person stands on the floor of the elevator, weight acts on the person where the direction of the person is downward. That person at rest so that there is must a normal force acts on the person, where the direction of the normal force is upward and the magnitude of the normal force same as the magnitude of the weight.

Newton's first law of motion – problems and solutions 1

Because the person is at rest in the elevator and the elevator moves at a constant speed (no acceleration), so there is no net force act on the person.

∑F = 0

N – w = 0

N = w

N = 800 Newton