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 slowly lower (to their chest) and then raise a barbell back to the starting position. They start off by using a 37.5 kg barbell. Joe is taller than Sam which means Joe's arms are 69.2 cm long while Sam's are 59.0 cm. Calculate the work done by Joe, WJoe, when he raises the barbell to finish one repetition. The acceleration due to gravity is 9.81 m/s2.

W Joe= J

Remember Sam also does the exercise. How does the amount of work Sam does, WSam, lifting the weight compare to Joe? Choose the correct operator from the list below.

1)W Sam= WJoe

2)W Sam> WJoe

3)WSam< W Joe

Explanation / Answer

To solve for the work of Joe you use:

First you have to convert your cm into meters (there are 100 cm= 1 m)

Joes Arms = 69.2 cm (1m/100 cm) = .692 m long

Sam's Arms = 59 cm (1m/ 100 cm) = .59 m long

Then you use the information given to you to plug into the equation below to solve for the work done for each.

W= Fd= m x g x d

So for Joe it would be W= (37.5 kg) (9.8 m/s^s) (.692 m)= 254.31 J

For Sam it would be W= (37.5 kg) (9.8 m/s^2)(.59 m)=216.83 J

By these two calculations it is obvious that for part b of your question will be that the work of sam will be less than the work of Joe.

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