Question

A man weighs 650 N. Inside a moving elevator, the floor exerts an upward force of 620 N on the man. What is the magnitude and direction of the man's acceleration?

Answer 1

Given that,

Weight of man, W= 650 N

Upward force by elevator, F= 620 N

a = ?

Since,

W = mg

m= W/g =650/9.81

m = 66.25 kg

Since,

F = ma

a = F/m

a = 620/66.25

a = 9.35 m/s²

Acceleration will be 9.35 m/s².

Since the force is in upward direction, it will accelerate the body in upward direction.

Answer 2

Answer:Man's acceleration is 0.452 $\frac{m}{s^{2}}$ in downward direction

Explanation:

Weight of man, W= 650 N

Normal force exerted by floor of elevator , N= 620 N

Since weight , W = mg

mass m= $\frac{W}{g}=\frac{650}{9.8}kg$

Using Newtons 2nd law

W-N= ma     where a= acceleration of man in the downward direction

=> 650-620=$\frac{650}{9.8}kg\times a$

=> a= 0.452 $\frac{m}{s^{2}}$ in downward direction