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Chapter 1: Q14DQ (page 356)

14. Why is it easier to hold a 10-kg dumbbell in your hand at your side than it is to hold it with your arm extended horizontally?

Short Answer

Expert verified

More force is required to hold the 10-kg dumbbell in the arm so it is easier to hold at the sides.

Step by step solution

01

Center of gravity

The center of gravity is the point on a body where the total weight of the body is concentrated.

02

Holding the dumbbell

when holding 10-kg dumbbell in shoulders, a torque will be generated. The torque consists of force F and the distance between the center of force and arm of force which is given by 蟿=F脳r.

The balancing torque equation is mgx where = Fd where x+d = r.

From the above equation, F=mgxd where x is the distance of the dumbbell. Increasing distance increases the exerted force given by the arm.

Therefore, it is easy to hold the dumbbell in the hand at the side than to hold in arm extended horizontally.

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