<span title="Physics....help....!!!plz...?">Physics....help....!!!plz...</span>

Question

A person in an elevetor suspends a 1.0 kg mass from a spring balance. what is the nature of the elevators motion when the balance reads 9.0N?9.8N?10.0N?

Answer 1

You can tell from the formula  Fg = m * (g + a)

Fg is the force you are given in Newtons(N)

m = 1 kg

g = 9.8 m/s^2

a = additional acceleration either up or down.

So when it is 9.8N the elevator is not accelerated (a=0), which means it is either stopped or moving with same velocity in any direction (either up or down in elevators).

When it is 9.0N it is accelerating downward (a = -0.8m/s^2). For example when you press ground floor and elevator starts moving and you feel you are a bit weightless. Or when you are going up and it stopping since you reached your floor.

When its 10.0N it is accelerating up. For example when you start to go up and you feel heavier. Or when you are going down and the elevator is stopping  (a = 0.2m/s^2)

Answer 2

For 9 N the motion &#039;ll be downward

For 9.8 N the motion &#039;ll be still

For 10 N the motion &#039;ll be upward

Answer 3

Let&#039;s make this easy and assume the force due to gravity to be 10 N/kg instead of the usual 9.8 N/kg. The accuracy is a bit less, but it&#039;s easier for explaining how it works.

If the mass is suspended and stationary, then the spring exerts a force equal to the weight of the mass. The mass is 1kg, so the spring must exert an upward force of 10N which exactly cancels out the weight, which is also 10N.

But, if the balance only reads 9N, that means there&#039;s a net force of 1N downwards (remember the mass weighs 10N)

Therefore the mass is accelerating downwards. Find the acceleration using F=ma

F = 1N, m=1kg, so a = 1 m/s^2.

The mass is in the elevator, so the elevator must be accelerating down at 1 m/s^2.

You can repeat the calculation for the other 2 cases.