A merry-go-round is a common piece of playground equipment. A 3.0-m-diameter merry-go-round with a mass of 250 kg is spinning at 20 rpm. John runs tangent to the merry-go-round at 5.0 m/s, in the same direction that it is turning, and jumps onto the outer edge. John's mass is 30 kg. What is the merry-go-round's angular velocity, in rpm, after John jumps on?

Question

anonymous · Answer

I've been using conservation of momentum:$$I_iomega_i+I_i \omega_i=I_f \omega_f+I_f \omega_f$$

I keep ending up with $$\omega=1.29 rad/s$$ which amounts to 12 rpm. It's telling me I'm wrong.

anonymous · Answer

I got 1.24rad/s or 11.84 rpm by keeping every number as it is and not rounding it off.
So I think you're absolutely right.

anonymous · Answer

I have the same numbers and Mastering Physics is telling me it's wrong