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Old Jan 17th 2014, 10:35 AM   #1
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take-off velocity during a vertical jump

Hello i need help here is my question.
i am 74 kg, and did a vertical jump with a displacement of 40.667 cm.
take-off velocity during a vertical jump-vertical-jump.png<<Here is the free body diagram i did.
My objective is to calculate the take off velocity during the vertical jump.
Can anyone teach me how to calculate this problem please?
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Old Jan 17th 2014, 11:43 AM   #2
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The energy of your initial velocity equals the potential energy gain at the pek of yuor jump. Thus:

(1/2)mv^2 = mgh

Solve for v:

v = sqrt(2gh)

Note that you mass doesn't matter.
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Old Jan 17th 2014, 07:10 PM   #3
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Originally Posted by ChipB View Post
The energy of your initial velocity equals the potential energy gain at the pek of yuor jump. Thus:

(1/2)mv^2 = mgh

Solve for v:

v = sqrt(2gh)

Note that you mass doesn't matter.
care to explain sqrt =)

Last edited by catknight; Jan 17th 2014 at 07:43 PM.
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Old Jan 17th 2014, 07:44 PM   #4
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Originally Posted by catknight View Post
care to explain sqrt =)
ho nvm i got it
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Old Jan 17th 2014, 11:16 PM   #5
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can any help me check if i am right?

v = sqrt ( 2 x 9.81N X 0.407M)
v = 3.026 m/s
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Old Jan 18th 2014, 07:13 AM   #6
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Originally Posted by catknight View Post
v = sqrt ( 2 x 9.81N X 0.407M)
v = 3.026 m/s
Check your calculator - I get 2.8 m/s. I think you might have used h = 0.467m instead of 0.407m.
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Old Jan 18th 2014, 07:17 AM   #7
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Originally Posted by ChipB View Post
Check your calculator - I get 2.8 m/s. I think you might have used h = 0.467m instead of 0.407m.
ho thanks for the info i think i key wrongly no my calulator
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