Extension Arm
Monday, June 28th, 2010Extension Arm
How much work does the weightlifter do to lift the barbell one time?
A weightlifter works out at the gym each day. Part of her routine is to lie on her back and lift a 42-kg barbell straight up from chest height to full arm extension, a distance of 0.51m . If the weightlifter does 16 repetitions a day, what total energy does she expend on lifting? Assume 25% efficiency. and How many 490 Calorie donuts can she eat a day to supply that energy? (explain how its done if possible)
Each day she does n*m*g*h work
So work = 16*42kg*9.8m/s^2*0.51m = 3359J
At 25% efficiency she expends 3359*4 = 13434J
Converting to Calories 1 Cal = 4.2kJ
so 13.434kJ/4.2kJ/Cal = 3.2 Cal
So she must consume 3.2/490 = 6.5x10^-3 donuts
How To: Arm Extension (Cybex)
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