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Q 34PE

College Physics (Urone)
Found in: Page 319

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Short Answer

Question: A father lifts his child as shown in Figure . What force should the upper leg muscle exert to lift the child at a constant speed?

The total force exerted by the upper leg muscle is 2254N.

See the step by step solution

Step by Step Solution

Step 1: Define the force

A force is an external factor that can change the rest or motion of a body. It has a size and a general direction.

Step 2: Free-body diagram

The diagram for the leg muscles is shown below:

Step 3: Calculation of the force on the upper leg muscle

The net torque about the pivot point which is knee, is zero in equilibrium. We can write


Here, the weight of the child is,

wchild=10×9.8=98 N

The weight of the leg is,

FQ×2=39.2×20+98×38FQ=39.2×20+98×382FQ=2254 N

Hence, the force is 2254N.

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