# momentum

posted by .

A playground merry-go-round has a disk-shaped platform that rotates with negligible friction about a vertical axis. The disk has a mass of 230 kg and a radius of 1.6 m. A 38- kg child rides at the center of the merry-go-round while a playmate sets it turning at 0.15rpm. If the child then walks along a radius to the outer edge of the disk, how fast will the disk be turning (in rpm)?

i am aware that another question has been posted that is exactly the same as this, but when i used that technique, it did not work for me, so i am posting this question again. like i said, i need to get this answer in RPM and NOT rad/s

• momentum -

Convert rpm to rad/s to do the problem using conservation of angular momentum. Covert back to rpm when you get the answer. The child increases the moment of inertia by walking to the outer edge of the disk. I assume you know the formula for the moment of inertia of the disk

• momentum -

i tried that, but i'm not getting the answer right
i did disk momentum=Iw
and boy momentum=m*rpm*2pi/60
then i set those two equal to each other and then changed the w back to rpm, but i'm not getting the right answer.

## Similar Questions

1. ### Physics

A large disk of mass M and radius R is spinning like a CD of merry-go-round - that is, about an axis perpendicular to the plane of the disk. It is rotating at an angular velocity ?
2. ### Physics

In a playground, there is a small merry-go-round of radius 1.20 m and mass 190 kg. Its radius of gyration (see Problem 85 of Chapter 10) is 91.0 cm. A child of mass 44.0 kg runs at a speed of 4.50 m/s along a path that is tangent to …
3. ### Physics

In a playground, there is a small merry-go-round of radius 1.20 m and mass 190 kg. Its radius of gyration (see Problem 85 of Chapter 10) is 91.0 cm. A child of mass 44.0 kg runs at a speed of 4.50 m/s along a path that is tangent to …
4. ### Physics

In a playground, there is a small merry-go-round of radius 1.20 m and mass 190 kg. Its radius of gyration (see Problem 85 of Chapter 10) is 91.0 cm. A child of mass 44.0 kg runs at a speed of 4.50 m/s along a path that is tangent to …
5. ### physics

A playground merry-go-round has a disk-shaped 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 merry-go-round while …
6. ### Physics

A playground merry-go-round has a disk-shaped 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 merry-go-round while …
7. ### physics

A children's merry-go-round in a park consists of a uniform 200kg disk rotating about a vertical axis. the radius of the disk is 6 m and a 100kg man is standing on the outer edge when the disk is rotating at a speed of 0.20rev/s. how …
8. ### physics

A playground merry-go-round has a disk-shaped 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 merry-go-round while …
9. ### Physics

1. A certain playground merry-go-round is essentially an 90-kg 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 merry-go-round is turning …
10. ### College Physics

A 40 kg child is standing on the edge of a merry-go-round in a playground. Before they were deemed too dangerous, these were quite common. They were just huge rotating platforms you could sit on while someone spun you around in uniform …

More Similar Questions