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(a) A block slides from rest down a wedge inclined at an angle 8 with the horizontal. There is friction between the block and the wedge. When the block reaches the bottom of the wedge, its kinetic energy is 3 J, and gravity has done + 10 J of work on the block. Which of the following describes the energy transfers in this system? (A) ∆E int , block (B) Frictional work on block by wedge = -7 J (C) Frictional work on wedge by block = + 7 J (D) ∆E int, block = + 7 J (b) Suppose the wedge is free to slide on a frictionless horizontal table (there is still friction between the block and the wedge). The block is again released from rest and reaches the bottom of the wedge with a kinetic energy K after gravity does work W g on the block. The masses of the block and the wedge are known. From this information, is it possible to calculate the speed of the wedge? (A) Yes, by applying conservation of momentum in the horizontal direction (B) No, because we do not know how much mechanical energy is lost due to friction (C) No, because conservation of momentum does not apply when frictional forces act (D) No, because the net external force on the system is not zero

(a) A block slides from rest down a wedge inclined at an angle 8 with the horizontal. There is friction between the block and the wedge. When the block reaches the bottom of   the wedge, its kinetic energy is 3 J, and gravity has done + 10 J of work on the block. Which of the following describes the energy transfers in this system?
(A) ∆Eint, block
(B) Frictional work on block by wedge = -7 J
(C) Frictional work on wedge by block = + 7 J
(D) ∆Eint, block = + 7 J
(b) Suppose the wedge is free to slide on a frictionless horizontal table (there is still friction between the block and the wedge). The block is again released from rest and reaches the bottom of the wedge with a kinetic energy K after gravity does work Wg  on the block. The masses of the block and the wedge are known. From this information, is it possible to calculate the speed of the wedge?
(A) Yes, by applying conservation of momentum in the horizontal direction
(B) No, because we do not know how much mechanical energy is lost due to friction
(C) No, because conservation of momentum does not apply when frictional forces act
(D) No, because the net external force on the system is not zero

Grade:upto college level

1 Answers

Navjyot Kalra
askIITians Faculty 654 Points
8 years ago
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