alleryStart learning →The same 75.0 kg man now rides the lift upward at a constant speed of 1 m/s. What does the scale read?
A825 N, more than his weight
B735 N, the same as his weight
C810 N, more than his weight
D660 N, less than his weight
Answer & Solution
Correct answer: B. 735 N, the same as his weight
1. For any constant velocity the change in velocity is zero, so the acceleration is zero.
2. The scale reading is the mass times the acceleration plus the mass times the acceleration due to gravity.
3. With zero acceleration the first term vanishes.
4. Substitute the values: (75.0 kg)(9.80 m/s^2) = 735 N.
5. That equals his weight, and it holds whether the lift moves up, moves down, or stands still.
_Source: OpenStax College Physics (CC BY 4.0), Ch 4 "Dynamics: Force and Newton's Laws of Motion", section 4.7 Further Applications of Newton's Laws of Motion_
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