Question

# Three objects are connected on a table as shown in above figure. The coefficient of kinetic friction between the block of mass and the table is . The objects have masses of , and and the pulleys are frictionless. (a) Draw a free body diagram of each object. (b) Determine the acceleration of each object, including its direction. (c) Determine the tensions in the two cords. What If? (d) If the tabletop were smooth, would the tensions increase, decrease, or remain the same? Explain.

Hard

## Solution

Verified by Toppr

## (a) The free-body diagrams for each object are given below. (b) Let represent the positive magnitude of the acceleration of , of the acceleration of , and of the acceleration of . Call the tension in the left cord and the tension in the cord on the right. For For andย  , givingย  . Forย  , givingย  . We have three simultaneous equations: ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย  ย ย ย ย ย ย ย ย ย ย ย ย ย ย ย  Add them up (this cancels out the tensions): ย ย ย ย ย ย ย ย ย ย ย  ย ย ย ย ย ย ย ย ย ย ย  , down for , left for , and up for (c) Nowย ย  ย ย ย ย ย ย ย ย ย  and ย ย ย ย ย ย ย ย  ย ย ย ย ย ย ย ย  (d) If the tabletop were smooth, friction disappears , and so the acceleration would become larger. For a larger acceleration, according to the equations above, the tensions change: ย ย ย ย ย ย ย ย  decreases. ย ย ย ย ย ย ย ย  increases.

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