Question

The model airplane is being spun at a speed of 20 m/s on a horizontal circle of radius 17 m. The mass of the plane is 0.86 kg. The person holding the guideline pulls it in until the radius becomes 13 m. The plane speeds up, and the tension in the guideline becomes four times greater. What is the net work done on the plane?

Answer 1

Well, conservation of momentum applies

I w1=Iw2

I =mr^2
w1=v/r=20/17 rad/sec
m(17)^2*20/17=m(13)^2 V/13

vfinal=20*17/13 m/s

now, figure change in Kinetic Energy
KEf-KEi=work
m(20^2)(4/13)=work

Answer 2

Thank you for helping me!