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Q5.35 A block of mass 15 kg is placed on a long trolley. The coefficient of static friction between the block and the trolley is 0.18. The trolley accelerates from rest with 0.5 m s-2 for 20 s and then moves with uniform velocity. Discuss the motion of the block as viewed by (a) a stationary observer on the ground.

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(a) Using Newton's second law of motion we can write :

                               F\ =\ ma

or                                  =\ 15\times0.5\ =\ 7.5\ N  Its direction is in the direction of motion of trolley.

                          The frictional force is     f\ =\ \mu mg

or                                                             =\ 0.18\times 15\times 10\ =\ 27\ N

Since the frictional force is greater than the applied force so the block will appear to be at rest when seen by any stationary person. 

Posted by

Devendra Khairwa

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