- #1
lizzyb
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Hi. I'm having difficulty answering three questions of my homework and hope someone will lend a hand. The questions seem beyond what we've had in class but I need to do them regardless.
Diving Board Problem
Consider a diving board:
I'm to find the force exerted on support A and support B. Givens: m_(board) and m_(person)
I know that the sum of the torques is 0, and looking at someone else's work on another webpage, I came up with:
F_b * 1m - m_(person)*g*4.4 - m_(board)*g*2.2 = 0
Anyway, solving for F_b using this equation came out wrong plus I still need to solve for F_a.
Work to Stop a Flywheel
Given a flywheel with radius r, moment of inertia I, and it's rotation rate (revolutions/sec), if a force of 4.3 N is applied tangentially to the flywheel to slow it down, how much work will be done by this force in brining the flywheel to a stop?
I know that W = delta KE = KE_f - KE_i
and that KE_r = (1/2) * I * (omega)^2,
now, rotation rate = 7.6 revolutions/sec = 7.6 * 2 * pi/sec = 47.7522 rads/sec
Thus KE_r = (1/2) * I * (47.7522)^2
Which looks good; but how do I fit the force applied to the flywheel in the W = KE_f - KE_i??
Thank you, Elizabeth
Diving Board Problem
Consider a diving board:
Code:
o/
[- 1m -][- 3.4m -]|_ <-- person at end of board
-------------------
| |
A B
I know that the sum of the torques is 0, and looking at someone else's work on another webpage, I came up with:
F_b * 1m - m_(person)*g*4.4 - m_(board)*g*2.2 = 0
Anyway, solving for F_b using this equation came out wrong plus I still need to solve for F_a.
Work to Stop a Flywheel
Given a flywheel with radius r, moment of inertia I, and it's rotation rate (revolutions/sec), if a force of 4.3 N is applied tangentially to the flywheel to slow it down, how much work will be done by this force in brining the flywheel to a stop?
I know that W = delta KE = KE_f - KE_i
and that KE_r = (1/2) * I * (omega)^2,
now, rotation rate = 7.6 revolutions/sec = 7.6 * 2 * pi/sec = 47.7522 rads/sec
Thus KE_r = (1/2) * I * (47.7522)^2
Which looks good; but how do I fit the force applied to the flywheel in the W = KE_f - KE_i??
Thank you, Elizabeth