4. [2 pts.] Conceptual question. Two identical blocks are pushed up frictionless

Question

4. [2 pts.] Conceptual question. Two identical blocks are pushed up frictionless inclines as shown. Consider the portion of the motion of block I during which it moves a distance L, and the portion of the motion of block 2 during which it moves a distance L2. Each block is displaced the same vertical distance Z L, The hand pushes parallel to the incline with same magnitude of force FRH in both cases. Block 2 moves at a decreasing speed. a. Is the absolute value of the work done by the hand on block 2 greater than, less than, or e b. Is the absolute value of the work done by the gravitational force on block 2 greater than, less than, or c. Use the work-kinetic energy theorem to determine whether the speed of block 1 increases, decreases, or absolute value of the work done by hand on block 1? Explain. equal to the work done by the gravitational force on block 1? Explain. remains constant as it moves the distance shown (Li). (Can it be determined based on the information provided?) Explain.

Explanation / Answer

a)

work done by hand on block2 isgreater than the work done by hand on block1 because the L2 > L1 , thought both reached the vertical heights are same  

b) work done by the gravitational force on block2 is equal to the work done by the gravitational force on block1

both are reaching the same height

c) work energy theorem is total workdone = change in kinetic energy

here if the block is moving downward the work done by the gravitational force results in the increasing in its kinetic but , the hand applieng force equal to the gravitatioanl force then the speed of the block remains same .

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