A 60 kg man stands on a spring scale in a lift. At someinstant, he finds that the scale reading has changedfrom 60 kg to 50 kg for a while and then comes back tooriginal mark. What should be concluded?a)The lift was in constant motion upwardsb)The lift was constant motion downwardsc)Lift while in motion downwards suddenly stoppedd)The lift while in motion upwards suddenly stopped.Correct answer is option 'D'. Can you explain this answer?

Question

Answer

Explanation:

The change in the reading of the spring scale indicates that there was a change in the forces acting on the man when the scale reading changed from 60 kg to 50 kg and then back to 60 kg. There are three possible scenarios that could have caused this change in the reading of the scale.

1. The lift was in constant motion upwards: In this scenario, the man would experience an increase in his weight as the lift moves upwards. Therefore, the scale reading would increase and not decrease. Hence, option 'A' is incorrect.

2. The lift was constant motion downwards: In this scenario, the man would experience a decrease in his weight as the lift moves downwards. Therefore, the scale reading would decrease. However, the scale reading would remain constant at 50 kg if the lift is moving at a constant velocity. Hence, option 'B' is incorrect.

3. Lift while in motion downwards suddenly stopped: In this scenario, the man would experience a sudden decrease in his weight when the lift stops. Therefore, the scale reading would decrease from 60 kg to 50 kg. When the lift starts moving again, the man would experience an increase in his weight, and the scale reading would return to 60 kg. Hence, option 'C' is incorrect.

Therefore, the correct option is 'D', which states that the lift while in motion upwards suddenly stopped. When the lift stops suddenly, the man would experience a sudden increase in his weight. Therefore, the scale reading would decrease from 60 kg to 50 kg. When the lift starts moving again, the man would experience a decrease in his weight, and the scale reading would return to 60 kg.

Conclusion:

Based on the change in the reading of the spring scale, it can be concluded that the lift while in motion upwards suddenly stopped.

Answer

Reading on the spring scale basically denotes the normal reaction received by a person from the ground.In this case person will receive normal reaction(N) in vertically upward direction and force of gravity(mg) will be in downward direction. Therefore N=50g;mg=60g .Here, mg−N=10g=+ve .Therefore body will accelerate in downward direction. So, D option is the correct

Answer

Option D is correct

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