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Rotational Motion Find g - Galileo Inclined Plane
Galileo measured the acceleration of gravity by rolling a sphere down an inclined plane. Suppose that, starting from rest, a sphere takes 1.6s to roll a distance distance of 3.00 m down a 20 degree inclined plane. What value of g can you deduce from this?
PE=KE(trans.)+KE (rot.)
I=2/5Mr^2
torque=force*distance
Torque=I*angular acceleration
-I've tried to use torque to solve for the acceleration down the plane, and this yielded a=5/7 * g *sin (theta)
I used:
distance=1/2at^2 to solve for a.
a=2.34375m/s^2
When this is plugged back in, I get:
2.34375=5/7 * g *sin (theta)
(2.34375*7)/5=3.28125
3.28125/sin(20)=9.59373
g= 9.59373 m/s2
[STRIKE]This is not close to the answer of 9.6, or the accepted value (9.81). I know I'm doing something significantly wrong, but I can't figure out exactly what the problem is. If anyone could point me in the right direction, I'd really appreciate it. Thanks.[/STRIKE]
The original problem had to do with an incorrect interpretation of the parallel-axis theorem. It should have been I=ICM+md2.
Homework Statement
Galileo measured the acceleration of gravity by rolling a sphere down an inclined plane. Suppose that, starting from rest, a sphere takes 1.6s to roll a distance distance of 3.00 m down a 20 degree inclined plane. What value of g can you deduce from this?
Homework Equations
PE=KE(trans.)+KE (rot.)
I=2/5Mr^2
torque=force*distance
Torque=I*angular acceleration
The Attempt at a Solution
-I've tried to use torque to solve for the acceleration down the plane, and this yielded a=5/7 * g *sin (theta)
I used:
distance=1/2at^2 to solve for a.
a=2.34375m/s^2
When this is plugged back in, I get:
2.34375=5/7 * g *sin (theta)
(2.34375*7)/5=3.28125
3.28125/sin(20)=9.59373
g= 9.59373 m/s2
[STRIKE]This is not close to the answer of 9.6, or the accepted value (9.81). I know I'm doing something significantly wrong, but I can't figure out exactly what the problem is. If anyone could point me in the right direction, I'd really appreciate it. Thanks.[/STRIKE]
The original problem had to do with an incorrect interpretation of the parallel-axis theorem. It should have been I=ICM+md2.
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