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)

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(4) 1200 N. Given: m=80 kg, a=5 m/s² upwards, g=10 m/s². Idea: the scale reads the normal force it pushes up with, not the weight. Newton's second law for the man: N-mg=ma. N=m(g+a). N=80×(10+5). N=80×15=1200 N. The reading is larger than the 800 N he weighs at rest, as it must be while the lift speeds upwards.

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)

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