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1
Q:

A man stands in a lift which accelerates upwards. The resultant reaction force on the floor of the lift is 

A) greater than the weight of the man B) less than the weight of the man
C) Same as the weight of the man D) Zero

Answer:   A) greater than the weight of the man



Explanation:

The weight of the man mg is acting on the floor. As the lift is moving up with an acceleration, say a, the man too in it is having this acceleration. The force producing this acceleration is ma. By Newton's third law, this force will have an equal reaction pressing the floor equal to ma. Therefore the total resultant reaction on the floor is mg+ma = m(g+a) which is mg, the weight of the man. So (a) is correct.

Subject: Physics
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