Posted by James on Sunday, June 17, 2012 at 5:56pm.
10. A yo-yo is made by wrapping a 2-m long string around a 500-g 10-cm diameter uniform disk. The string is fastened to the ceiling, and the yo-yo is released. What is the tension in the string as the yo-yo falls?
The answer is B. How do I get this answer? I'm having trouble figuring out why tension would be less than (mg). Thank you in advance.
Physics - Damon, Sunday, June 17, 2012 at 6:37pm
Tension = T
force up = T
force down = m g
m g - T = m a
torque = I * angular acceleration
T * R = I alpha = I a/R
but I for disk = (1/2) m R^2
T R = (1/2) m R a
T = (1/2) m a interesting :)
m g - (1/2) m a = m a
g = (3/2) a
a = (2/3) g
T = (1/2) m (2/3) g = (1/3) m g
= 1.63 N or B
Physics - Elena, Sunday, June 17, 2012 at 7:06pm
T-tension, M –torque,
I = mR²/2 -moment of inertia of disc
I•a/R = T•R,
m•2T/m = mg-T,
T=mg/3 =0.5•9.8/3 = 1.63
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