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Q 34PE

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College Physics (Urone)
Found in: Page 319
College Physics (Urone)

College Physics (Urone)

Book edition 1st Edition
Author(s) Paul Peter Urone
Pages 1272 pages
ISBN 9781938168000

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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

TABLE OF CONTENTS :
TABLE OF CONTENTS

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

FQ×2=wleg×20+wchild×38

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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