## A L d26dt2 et L d6dt2 er29c

Note that the speed of the particle v is given by the expression v = L (d6/dt) (2.9d)

Example 2.4. Arm Movements in Aerobics. An aerobic instructor abducts her arm from downward vertical position to horizontal position at shoulder length in 0.6 seconds (s), at constant rate (Fig. 2.7a). Determine the velocity and acceleration of her elbow. Assume that the length of her upper arm is 0.38 m.

Solution: Since 0.6 s was required to traverse an angle of ^/2 radians at constant rate d6/dt = ^/1.2 d26/dt2 = 0

Thus, using Eqn. 2.9, velocity and acceleration of the elbow can be expressed as v = 0.99 (m/s) et a = -2.60 (m/s2) er

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The use of dumbbells gives you a much more comprehensive strengthening effect because the workout engages your stabilizer muscles, in addition to the muscle you may be pin-pointing. Without all of the belts and artificial stabilizers of a machine, you also engage your core muscles, which are your body's natural stabilizers.

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