A man weighs 80 kg. He stands on a weighing scale in a lift which is moving upwards with a uniform acceleration of 5 m/s2. What would be the reading on the scale. (g = 10 m/s2)

Q: A man weighs 80 kg. He stands on a weighing scale in a lift which is moving upwards with a uniform acceleration of 5 m/s2 . What would be the reading on the scale. (g = 10 m/s2)

(a) 400 N

(b) 800 N

(c)1200 N

(d) zero

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Ans: (c)

Sol: R – m g = m a

R = mg + ma

R = 80 × 10 + 80 × 5

R = 1200 N