Two friends, Joe and Sam, go to the gym together to strength train. They decide

Question

Two friends, Joe and Sam, go to the gym together to strength train. They decide to start off with an exercise called flat bench press. Lying flat on a bench with their arms in an extended position, they slow lower (to their chest) and then raise a barbell back to the starting position. They start off by using a 36.0 kg barbell. Joe is taller than Sam which means Joe's arms are 67.2 cm long while Sam's are 60.6 cm. Calculate the work done by Joe, W_Joe, when he raises the barbell to finish one repetition. The acceleration due to gravity is 9.81 m/s^2. W_Joe = J Remember Sam also does the exercise. How does the amount of work Sam does, W_Sam, lifting the weight compare to Joe? Choose the correct operator from the list below compare to Joe? Choose the correct operator from the list below. W_Sam = W_Joe W_Sam > W_Joe W_Sam

Explanation / Answer

m = mass= 36 kg

distance travelled by Joe,d = arm length = 67.2 cm

distance travelled by Sam,d' = arm length = 60.6 cm

g= 9.81

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work done by Joe ,W_joe = Force*displacement

W_joe = mg*d

= 36*9.81*67.2*10-2 = 237.32 J

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work done by Sam , W_sam = 36*9.81*60.6*10-2 = 214 J

W_sam< W_Joe

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