Physics · Circular Motion & Momentum
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A man stands in a lift that is accelerating vertically downwards. Which statement describes the force exerted by the man on the floor?
- A
It is equal to the weight of the man.
- B
It is greater than the force exerted by the floor on the man.
- C
It is less than the force exerted by the floor on the man.
- D
It is less than the weight of the man.
As the lift is accelerating vertically downward so (g-a). The apparent weight of a man would become less than the actual weight.
F=W-R
ma=mg-R
R=mg-ma
R= m(g-a)
If the lift would be moving upward then (g+a), both g and acceleration would be parallel
F=R-W
ma=R-mg
ma+mg=R
R=m(a+g)
In the case of acceleration, the weight and the exerted force can't be equal. The weight of man and exerted force will be equal if the lift is at rest or moving with constant speed.
The floor would apply a force on a man equal to the weight of a man.
This option is incorrect as the force exerted by the man is affected by the lift's acceleration.
This option is incorrect as the force exerted by the man is not greater than the force exerted by the floor in this scenario.
This option is incorrect as the force exerted by the man is not less than the force exerted by the floor in this scenario.
When in a lift accelerating downwards, the force exerted by the man on the floor is less than the weight of the man due to the lift's acceleration affecting the apparent weight.
Tagged under Physics · Circular Motion & Momentum · 2018