PHYSICS (HELP)
posted by Anonymous .
A playground merrygoround has a radius of R= 2 m and has a moment of inertia Icm= 9×103kg⋅m2 about a vertical axis passing through the center of mass. There is negligible friction about this axis. Two children each of mass m= 20kg are standing on opposite sides at a distance ro= 1.2m from the central axis. The merrygoround is initially at rest. A person on the ground applies a constant tangential force of F= 2.0×102N at the rim of the merrygoround for a time Δt= 18s . For your calculations, assume the children to be point masses.
(a) What is the angular acceleration α of the merrygoround? (in rad/s2)
α=
(b) What is the angular velocity ωfinal of the merrygoround when the person stopped applying the force? (in rad/s)
ωfinal=
(c) What average power Pavg does the person put out while pushing the merrygoround? (in Watts)
Pavg=
(d) What is the rotational kinetic energy R.K.Efinal of the merrygoround when the person stopped applying the force? (in kg⋅m2/s2)
R.K.Efinal=

PHYSICS (HELP) 
Elena
R=2 m, Ic=9000 kg•m², r₀=1.2 m, m=20 kg, F=200 N, Δt=18 s.
I=Ic+2I₀=Ic+2m r₀² =
=9000+2•20•1.2²=9057.6 kg•m².
M=Iα
α=M/I=FR/I =200•2/9057.6 = 0.044 rad/s²
ω=α•Δt =0.044•18=0.792=0.8 rad/s
P=Fv=P ωR = 200•0.8•2 = 320 W.
KE=Iω²/2 = 9057.6•0.8²/2 = 2898.4 J. 
PHYSICS (HELP) 
Anonymous
The power is wrong

PHYSICS (HELP) 
Greco
power is
KE=Iù²/2 = 9000•0.8²/2 = 2880 J.
(Whitout the children)
Respond to this Question
Similar Questions

physics
A playground merrygoround has a diskshaped platform that rotates with negligible friction about a vertical axis. The disk has a mass of 240 kg and a radius of 1.4 m. A 33 kg child rides at the center of the merrygoround while … 
Physics
A playground merrygoround has a diskshaped platform that rotates with negligible friction about a vertical axis. The disk has a mass of 240 kg and a radius of 1.4 m. A 33 kg child rides at the center of the merrygoround while … 
physics
A playground merrygoround has a diskshaped platform that rotates with negligible friction about a vertical axis. The disk has a mass of 210 kg and a radius of 1.8 m. A 35 kg child rides at the center of the merrygoround while … 
Physics Inertia : Merrygoround
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 … 
Physics
1. A certain playground merrygoround is essentially an 90kg iron disk 2.0 m in radius. Two children, each with a mass of 46 kg, are originally standing on opposite sides of the disk near its outer edge. The merrygoround is turning … 
Physics Please help!
In each of the following cases, the mass is 7.99 kg and the radius is 7.50 cm. (a) What is the moment of inertia (kg/m2 ) of a solid cylinder rotating about an axis parallel to the symmetry axis but passing through the edge of the … 
Physics
An engineer has an oddshaped 11.4 kg object and needs to find its rotational inertia about an axis through its center of mass. The object is supported on a wire stretched along the desired axis. The wire has a torsion constant κ … 
Physics Classical Mechanics
A playground merrygoround has a radius of R= 2 m and has a moment of inertia Icm= 9×103kg⋅m2 about a vertical axis passing through the center of mass. There is negligible friction about this axis. Two children each of mass … 
Physics
A hollow sphere has a mass of 15 kg, an inner radius of 12 cm and an outer radius of 18 cm. What is the rotational inertia (moment of inertia) of the sphere about an axis passing through its center? 
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 …