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A person jumps from the roof...
A person jumps from the roof of a house 3.9 m high. When he strikes the ground below, he bends his knees so that his torso decelerates over an approximate distance of 0.73 m.
- PART A If the mass of his torso (excluding his legs) is 40 kg, find his velocity just before his feet strike the ground.
- PART B: If the mass of his torso (excluding his legs) is 40 kg, find the magnitude of the average force exerted on his torso by his legs during deceleration.
I've done PART A, and got 8.7 m/s. (or [tex]\sqrt{2*9.8*3.9}[/tex]))
I tried to get the acceleration during the deceleration by using the equation
(vf)^2 = (v0)^2-2ad
2a(.73m) = (8.7m/s)^2
a = 52.35
And multiplied the acceleration by the mass (40 kg) to get 2094 N,
but the program says I'm wrong! What am I doing wrong here?
Homework Statement
A person jumps from the roof of a house 3.9 m high. When he strikes the ground below, he bends his knees so that his torso decelerates over an approximate distance of 0.73 m.
- PART A If the mass of his torso (excluding his legs) is 40 kg, find his velocity just before his feet strike the ground.
- PART B: If the mass of his torso (excluding his legs) is 40 kg, find the magnitude of the average force exerted on his torso by his legs during deceleration.
Homework Equations
The Attempt at a Solution
I've done PART A, and got 8.7 m/s. (or [tex]\sqrt{2*9.8*3.9}[/tex]))
I tried to get the acceleration during the deceleration by using the equation
(vf)^2 = (v0)^2-2ad
2a(.73m) = (8.7m/s)^2
a = 52.35
And multiplied the acceleration by the mass (40 kg) to get 2094 N,
but the program says I'm wrong! What am I doing wrong here?