Posted by **Sasha** on Monday, November 29, 2010 at 2:05am.

A yo-yo is made of two solid cylindrical disks, each of mass 0.053 kg and diameter 0.073 m, joined by a (concentric) thin solid cylindrical hub of mass 0.0052 kg and diameter 0.012 m. Use conservation of energy to calculate the linear speed of the yo-yo when it reaches the end of its 1.1 m long string, if it is released from rest.

- physics -
**drwls**, Monday, November 29, 2010 at 3:02am
The decrease in potential energy equals the increase in kinetic energy, most of which is rotational KE. First compute the moment of inertia of the yo-yo, I.

If it falls a distance L (which is 1.1 m in this case) then

M g L = (1/2) I w^2 + (1/2) M V^2

The angular rotation rate w can be replaced by V/r, where r is the radius of the cylindrical hub. Then solve for V.

V^2[1 + I/(Mr^2)] = 2*g*L

Take it from there.

- physics -
**Sasha**, Wednesday, December 1, 2010 at 11:06pm
I still don't get it.Moment of inertia of the yo-yo is 1/2 mr^2: 1/2(.053kg)(.0365^2) + 1/2(.0052kg)(.006^2)

which equals to 3.54*10^-5

so i plugged that into = square root of (2*9.8*1.1)/ (1 + (3.54*10^-5/(mr^2))

and i got something like 4.6 which is not a correct answer. Can you help me clarify this question please?

## Answer this Question

## Related Questions

- math - A metal solid made up of a cylindrical bar fixed onto a cube. The ...
- solid mensuration - A cylindrical tin can holding 2 gal.has its height equal to ...
- GEOMETRY - A cylindrical tank if 8 ft. in diameter and 20 ft tall. how many ...
- INTRO TO PHYSICS - Each of the following objects has a radius of 0.174 m and a ...
- Physics - Four objects - a hoop, a solid cylinder, a solid sphere, and a thin, ...
- physics - A thin, light string is wrapped around the rim of a 4.00kg solid ...
- physics - an atwoods machine has a solid cylindrical pulley with a mass of 200g ...
- arithmetic - if the internal diameter of a cylindrical iron piep is 2.8 cm . If ...
- maths-surface area - there is a groove which is in a cylindrical form and is ...
- maths-surface area - Cylindrical groove is made in a cylindrical piece of wood ...

More Related Questions