A disk with a red (inner) and green (outer) block attached to it is spinning at
ID: 2259250 • Letter: A
Question
A disk with a red (inner) and green (outer) block attached to it is spinning at constant angular acceleration. the disk has a radius of 10 cm and a mass of 1.2 kg; the green block has mass of .5 kg and is 8 cm from the center of the disk; the red disk has a mass of .8 kg and is 4 cm from the center of the disk.
a) Is there a net force on the green block? Explain
b) Is there a net torque on the red block? Explain
c) Is there a net torque on the disk? Explain
d) Calculate the moment of inertia of the system (disk and block)
Explanation / Answer
a) Is there a net force on the green block? Explain
there is a net acceleration of the green block which is given by w^2*R
so there must be a net force (by newtons 2nd law of motion) which is given by m*a=mw^2R
so there is net force
b) Is there a net force on the red block? Explain
there is a net acceleration of the red block which is given by w^2*R
so there must be a net force (by newtons 2nd law of motion) which is given by m*a=mw^2R
so there is net force
c) Is there a net torque on the disk? Explain
same logic apply here
there is a net angular acceleration of the disc which is given by w
so there must be a net torque (by newtons 2nd law of motion) which is given by I*alpha
so there is net torque
d) Calculate the moment of inertia of the system (disk and block)
I = 0.5*1.2*0.1^2 +0.5*0.08^2 +0.8*0.04^2=0.01048 Kg-m^2
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