Question

The apparent weight of a person inside a lift is w1 when lift moves up with a certain acceleration and is w2 when lift moves down with same acceleration. The weight of the person when lift moves up with constant speed is

• A. $ \frac{{{w}_{1}}+{{w}_{2}}}{2} $
• B. $ \frac{{{w}_{1}}-{{w}_{2}}}{2} $
• C. $ 2{{w}_{1}} $
• D. $ 2{{w}_{2}} $

Answer 1

The Correct Option is A

When lift moves up with constant acceleration a, then $ {{w}_{1}}-mg=ma $ ?(i) When lift moves down with constant acceleration a, then $ mg-{{w}_{2}}=ma $ ?(ii) From Eqs. (i) and (ii), we get $ {{w}_{1}}+{{w}_{2}}=2mg $ ?(iii) When lift moves up with constant speed, its acceleration is zero.So, $ w-mg=0 $ or $ w=mg $ (iv) From Eqs. (iii) and (iv) $ {{w}_{1}}+{{w}_{2}}=2w $ or $ w=\frac{{{w}_{1}}+{{w}_{2}}}{2} $