A 60 kg woman in an elevator is accelerating upward at a rate of 1.2 m/s2...?

Question

What is the new force acting upon the woman?
What is the gravitational force acting upon the woman?
What is the normal force pushing upward on the woman's feet?
Can someone check my answers? I got 0 N, 588N, and 516 N

the first question was actually net force instead of new

Answer 1

If you got 0N for the first part that is incorrect. Think about it logically, If she is being pushed up by the elevator, she will feel heavier, not lighter, so the force must be larger than what she would experience from Gravity alone. For every action there is an equal and opposite reaction. so the gravitational force of the woman on the floor of the elevator, will be added to the acceleration force of the elevator floor on the woman, not subtracted, even though it seems that they are acting in opposite directions. Force = Mass x Accelaration

so the force from the elevator's acceleration will be:
1.2m/s/s x 60kg = 72 Newtons

The gravitational force will be:

9.8m/s/s x 60kg = 588 Newtons

The net force acting on the woman will be:
588N + 72N = 660 Newtons.

So while the elevator is accelerating upwards, the woman will feel heavier:

660N / 9.8m/s/s = 67.3 kg

If the elevator accelerated downwards, the woman would feel lighter. If the elevator dropped at the same rate as the acceleration due to gravity, then the woman would feel weightless!

Answer 2

net force acting upon the woman suppose to be zero because the woman still in contact with floor and does not 'float'(means there is no buoyant force acting upon the woman.)

gravitational force = mg = 60 x 9.81 = 588.6 N (acting downwards)

F' = force acting upwards, F = force acting downwards
normal force = F' - F = m(a' - a)
= 60(1.2 - 9.81)
= -516.6 N(acting upwards)

Answer 3

i think your last answer is wrong .. the gravitational force is the mass times 9.8m/s2 right? and thats the normal force when shes standing on flat ground .. since shes accelerating upward the force should increase not decrease so i think its 60 x (9.8+1.2) = 660N

Answer 4

Now Martin, that is a great question. My hope is that you find your answer. Glad she is not me.