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GodPlaysDice
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Homework Statement
I have tried this thrice now, to no avail. Please help me. Here is the problem:
"In the figure, block 1 has mass m1 = 430 g, block 2 has mass m2 = 580 g, and the pulley is on a frictionless horizontal axle and has radius R = 4.9 cm. When released from rest, block 2 falls 74 cm in 5.0 s (without the cord slipping on the pulley). What is the pulley's rotational inertia? Caution: Try to avoid rounding off answers along the way to the solution. Use g = 9.81 m/s^2."
EDIT:
Both blocks are moving vertically, the lighter one is being raised by the heavier one by means of the pulley.
That centimeter difference is probably throwing everything in my calculations out of wack. I'll see if that was the problem. Thank you.
Homework Equations
F = ma
τ = Iω
a = Rα
Δx = Vot + 0.5at2
ω = ωo + αt
The Attempt at a Solution
Here is my attempt (one of many):
(I converted everything into SI base units)
I first found the acceleration:
Δx = 0.75
0.75 = 0.5a(5)
and found that a = 0.3
Next, I found α:
a = Rα
α = 6.1224
Then ω:
ω = 0 + 6.1224(5)
ω = 30.6
Next I drew a free body diagram for mass 2 and an extended FBD for the pulley and wrote the 2nd law equations for each assuming that the direction of the motion of mass 2 is positive.
Pulley:
(tension is T)
T = Iα
Block:
mg - T = ma
I added the two equations, yielding:
mg = Iα + ma
I plugged in the numbers, and solved for I:
I =
but the website I'm using is telling me I'm wrong.
I must know WHY?!
Thank you for any light you may shed on my errors.
Homework Statement
Homework Equations
The Attempt at a Solution
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