# physics

posted by .

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 -

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 -

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?

## Similar Questions

1. ### physics

A thin, light string is wrapped around the rim of a 4.00kg solid uniform disk that is 30.0cm in diameter. A person pulls on the string with a constant force of 100N tangent to the disk. Find the linear acceleration of its center of …
2. ### Physics

Blocks of mass m1 and m2 are connected by a massless string that passes over a frictionless pulley. Mass m1 slides on a frictionless surface. Mass m2 is released while the blocks are at rest. The pulley is a solid disk with a mass …
3. ### Physics

Four objects - a hoop, a solid cylinder, a solid sphere, and a thin, spherical shell - each has a mass of 4.59 kg and a radius of 0.252 m. (a) Find the moment of inertia for each object as it rotates about the axes shown in the table …
4. ### physics

an atwoods machine has a solid cylindrical pulley with a mass of 200g and a radius of 10cm. a 1.2 kg mass is hung on one side and a 1.1kg mass on the other side, find the acceleration of the two masses and the itme for them to travel …
5. ### solid mensuration

A cylindrical tin can holding 2 gal.has its height equal to the diameter of its base.Another cylindrical tin can with the same capacity has its height equal to twice the diameter of its base. Find the ratio of the amount of tin required …
6. ### INTRO TO PHYSICS

Each of the following objects has a radius of 0.174 m and a mass of 2.16 kg, and each rotates about an axis through its center (as in the table below) with an angular speed of 37.3 rad/s. Find the magnitude of the angular momentum …
7. ### maths-surface area

there is a groove which is in a cylindrical form and is made in a cylindrical piece of wood of length 17.5cm. The groove is filled with graphite and the cylindrical graphite block is of same length as that of wooden piece. If the diameter …
8. ### GEOMETRY

A cylindrical tank if 8 ft. in diameter and 20 ft tall. how many gallons of paint are needed to paint the tank if one gallon covers 200 sq ft ?
9. ### arithmetic

if the internal diameter of a cylindrical iron piep is 2.8 cm . If the pipe is melted uniformly by 1 mm then it formed a cylindrical rod ,find the diameter of the new rod?
10. ### math

A metal solid made up of a cylindrical bar fixed onto a cube. The cylindrical bar fixed onto a cube. The cylindrical bar is 20 cm long and has a diameter of 7 cm. Each side of the cube is 9 cm long. The surface of the solid was painted. …

More Similar Questions