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 34.5 kg barbell. Joe is taller than Sam which means Joe's arms are 67.8 cm long while Sam's are 59.8 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.

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.

Explanation / Answer

Well, as you might have learned in physics, Work = Force applied over a specific Distance. So the equation for Work is: Work = Force (Newtons) x Distance (Meters) The question asks you to calculate the work done by Joe. You'll need to change the 34.5kg into Newtons. A Newton is the unit for force, and is defined as a kg*m/s^2. To do this, you'll multiply 34.5 by 9.81. This will give you part of your equation. The distance part must be in meters. The problem tells you that Joe's arms are 67.8 cm long. You can assume, that he'll be moving the weight over that distance. So, convert 67.8 cm into meters, and you have the second required part to your above equation. Solve for work! For the second part of your question, consider the fact that Sam's arms are shorter than Joe's arms. If you look at your equation (W=FxD) what happens to work when the distance variable is less? Is it a direct relationship? I hope this helps! Good luck!

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