Physics Inertia : Merrygoround
posted by HELP ME!! .
A playground merrygoround of radius 1.96 m has a moment of inertia 335 kg m2 and is rotating at 12.3 rev/min. A child with mass 43.1 kg jumps on the edge of the merrygoround. What is the new moment of inertia of the merrygoround and child, together? Answer in units of kg m2.

Physics Inertia : Merrygoround 
bobpursley
add them: Inew=335 kg m^2+43.5*1.96^2 kg m^2

Physics Inertia : Merrygoround 
HELP ME!!
Thank you, but what equation do you use? I cant seem to get the correct answer.What happens to the rev/min? Is it: inertia+child mass*radius^2

Physics Inertia : Merrygoround 
bobpursley
The rev/min is not needed.
here is the equation:
momentofINertiatotal=momentinertiaMerryGoRound + momentinertiaKid.
Then you add them.
That is it. Now, if the problem goes on, you may need to find what the new angular speed is, but that is a different problem, you didn't ask that. 
Physics Inertia : Merrygoround 
nora
if you want to find the final angular speed, wf, you take:
momentinertiaMerryGoRound(initial angular speed) = (momentinertiaMerryGoRound + momentinertiaKid)(wf)
then solve for wf 
Physics Inertia : Merrygoround 
John
Correct

Physics Inertia : Merrygoround 
Ted
What is the moment of inertia of the kid?
Respond to this Question
Similar Questions

physics
A merry go round in the park has a radius of 1.8 m and a rotational inertia of 900 kgm^2. A child pushes the merry go round with a constant force of 80 N applied at the edge and parrallel to the edge. A frictional torque of 12 Nm … 
Physics: merrygoround question
A playground merrygoround of radius 1.92 m has a moment of inertia 411 kg m2 and is rotating at 10.4 rev/min. A child with mass 38.3 kg jumps on the edge of the merrygoround. Assuming that the boy's initial speed is negligible, … 
Physics
A merrygoround is rotating at 4.775 revs/min with a 45 kg child on the outer edge. The radius is 2.0 m. The child moves to the centre of the merry go round. What is the final angular velocity of the merry go round. The moment of … 
physics
A merrygoround in a playground has a mass of 200 kg and radius of 1.50 m. You apply a force F = 23 N tangentially to the edge of the merrygoround for a time of 6.5 s. The moment of inertia of the merrygoround is 1/2(mR2). What … 
Physics
A playground merrygoround of radius R = 2.15 m has a moment of inertia of I = 256 kg * m2 and is rotating at 10.9 revolutions/min about a frictionless vertical axle. Facing the axle, a 29.6 kg child hops onto the merrygoround and … 
physics
A playground merrygoround has a radius 2.6 m and a rotational inertia 83 kg.m^2. When the merrygoround is at rest, a child with mass 27 runs with speed 4.3 along a line tangent to the rim and jumps on. The angular velocity of the … 
Physics
A 24.5kg child is standing on the outer edge of a merrygoround which has moment of inertia 989 kg • m2 and radius 2.40 m. The entire system is initially rotating at 0.180 rev/s. Find the angular velocity if the child moves to … 
physics
A playground merrygoround of radius 2.00 m has a moment of inertia I = 255 kg·m2 and is rotating about a frictionless vertical axle. As a child of mass 25.0 kg stands at a distance of 1.00 m from the axle, the system (merrygoround … 
Physics
A playground merrygoround of radius R = 1.92m has a moment of inertia of I = 221kgm^2 and is rotating at 14.0rev/min about a frictionless vertical axle. Facing the axle, a 29.8kg child hops onto the merrygoround and manages to … 
physics
A playground merrygoround of radius R = 1.1 m has a moment of inertia of I = 280 kg*m^2. and is rotating at a rate of ω = 9 rev/min around a frictionless vertical axis. Facing the axle, a 37 kg child hops onto the merrygoround …