A cord is used to lower vertically a block of mass M a distance d at a constant downward acceleration of g/4. Then the work done by the cord on the block is :
Correct answer: D. -3Mgd / 4
- A. Mgd/4
- B. 3 Mgd/4
- C. Mgd
- D. -3Mgd / 4
Explanation
Option D is correct as :When the block moves vertically downward with acceleration g/4 the tension in the cord is:T=M(g-g/4)=3Mg/4Work done by cord = F.S cosθ As tension is acting upwards and the block is moving downwards the angle will be 180Work=(3Mg/4)X(d)Xcos(180)Work Done= -3Mgd/4
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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.
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