Question 22: A boy holds a 40-N weight at arm's length for 10 seconds. His arm is 1.5m above the ground. The work done by the force of the boy on the weight while he is holding it is: (Work, Power & Energy, work done by constant and variable forces)
Correct answer: A. 0 j
- A. 0 j
- B. 90 j
- C. 60 j
- D. 40 j
Explanation
Correct Answer: (a) 0 J Explanation:Work (W) = F x dWhile the boy exerts force (40 N), the weight doesn't move any distance (d = 0), so W = 40 N x 0 m = 0 J.Incorrect Options:(b) 90 J: This option confuses potential energy gain (40 N x 1.5 m = 60 J) with work done, which requires actual displacement.(c) 60 J: Same mistake as (b) - calculating potential energy instead of work.(d) 40 J: Considers only the force applied, ignoring the lack of displacement needed for work to be done.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
Practise Work and Energy
748 free Work and Energy MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Physics questions like this
Physics is on 16 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Work and Energy questions
Question 21: One megawatt hour (MWh) is equal to: (Work, Power & Energy, power and energy)
19) If velocity is doubled, then: (Work, Power & Energy, work energy principal)
18) Gravitational potential energy (PE) of a body can be found by: (Work, Power & Energy, absolute potential energy)
Question 27: A boat moving at constant speed v through still water experiences total frictional drag F. What is the power developed by the boat? (Work, Power & Energy, power and energy)
Question 28: When two protons are brought close together, what happens to their potential energy? (Work, Power & Energy, interconversion of potential and kinetic energy)
38. Solar energy conversion cell: (Work, Power & Energy, renewable energy resources)