A 70 kg man standing on a weighing scale in a lift which is movinga upward with unifor- speed of 10m-s2-b downward with uniform acceleration of 5m-s2c upward with a uniform acceleration of 5m-s2- the reading of the scale in each case-

Mass of man = 70 Kg #10; #10;(A) upward wih uniform acceleration means inertial frame of #10;reference. #10; #10;So, reading on weighing scale = norm ...

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Byju's Answer

Standard X

Physics

Apparent Weight

A 70 kg man...

Question

A $70$ kg man standing on a weighing scale in a lift which is moving a) upward with a uniform speed of $10 m / s$ , b) downward with a uniform acceleration of $5 m / s^{2}$ , c) upward with a uniform acceleration of $5 m / s^{2}$ . The reading of the scale in each case?

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Solution

Mass of man = 70 kg
(a) upward wih uniform speed means the inertial frame of reference.
Normal reaction = mg = 700 N.
So, reading on weighing scale = 70 kg.
(b) body moves downward with uniform acceleration 5 m/s². It means the body is present in a non-intertial frame of reference for applying Newton's law use 'Puedo force'.
Hence, the Pseudo force acts upward.
Hence, normal reaction = m(g - a)
= 70( 10 - 5)
= 70×5 = 350 N.
So, reading on weighing scale = 35 kg.
(c) upwards with uniform acceleration 5 m/s²
Hence, Pseudo force act downward. e.g ma (↓)
Normal reaction = mg + ma
= 70( 10 + 5)
= 70×15 = 1050 N
Hence, reading on weighing scale = 105 Kg

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A 70 kg man standing on a weighing scale in a lift which is moving a) upward with a uniform speed of 10m/s, b) downward with a uniform acceleration of 5m/s2, c) upward with a uniform acceleration of 5m/s2. The reading of the scale in each case?

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