Hi everyone,(adsbygoogle = window.adsbygoogle || []).push({});

I am stuck on two fairly easy questions that I hope someone will be able to help me with.

Questions:

1) How much angular impulse must be supplied by the hamstrings to bring a leg swinging at 8 rad/s to a stop, given that the leg's moment of inertia is 0.7 kg-m^2 ?

my solution:

angular impulse = change in angular momentum

Tt = Iw2 - Iw1 (the numbers 2 & 1 are supposed to be subscripts standing for final and initial; I=moment of inertia; w=angular velocity)

Tt = 0 - (.7)(8)

= -5.6 kg-m^2/s

what did I do wrong?

2) A 7.27kg shot makes seven complete revolutions during its 2.5 second flight. If its radius of gyration is 2.54 cm, what is its angular momentum?

my solution:

H = mk^2w (m=mass; k=radius of gyration; w=angular velocity; H = angular momentum)

7 revolutions = (360degrees x 7)/57.3

= 43.979 rad

H = (7.27)(.0254^2)(43.979/2.5sec)

= .0825 kg-m^2/s

what did I do wrong?

thanks.

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# Homework Help: Angular impulse and angular momentum questions

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