This is the problem for number 33 from chapter four : An 80 kg stuntman jumps fr

Question

This is the problem for number 33 from chapter four : An 80 kg stuntman jumps from a windowof a building situated 30 m above acatching net. Assuming air resistance exerts a 100-N force on thestuntman as he falls, determine his velocity just before he hitsthe net. I am having trouble figuring out which equations to use tosolve the problem. I am getting mixed up because it does notinclude acceleration. Also, is the net force the same as force? Andin this problem is my net force negative or is that the technicalform of writing it?
This is the problem for number 33 from chapter four : An 80 kg stuntman jumps from a windowof a building situated 30 m above acatching net. Assuming air resistance exerts a 100-N force on thestuntman as he falls, determine his velocity just before he hitsthe net. I am having trouble figuring out which equations to use tosolve the problem. I am getting mixed up because it does notinclude acceleration. Also, is the net force the same as force? Andin this problem is my net force negative or is that the technicalform of writing it?

Explanation / Answer

You're going to want to first find the net force on the stuntman,which is going to be force of gravity, minus force of airresistance F gravity is going to be 80kg * 9.8 m/s^2 = 784 N 784N - 100N = 684N = net force of stuntman now that you know the force, if you divide by his mass you'll findthe net acceleration: 684 / 80 = 8.55 m/s^2 now just use the kinematics equation: Vf ^2 = Vi ^2 + 2*a*d Vf^2 = 0 + 2 * 8.55 * 30 Vf^2 = 513 Vf = sqrt(513) which is about 22.649 m/s

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