High School

1. Compare these objects:

Object Alpha is a hoop of mass 55 kg and radius 0.24 m.

Object Bravo is a disk of mass 86 kg and radius 0.24 m.

Object Charlie is a sphere of mass 112 kg and radius 0.24 m.

a) Calculate the rotational inertias of each object.

b) Which object would win a race down an inclined plane?

Answer :

Answer

I = 3.168

I = 2.48

I = 2.58

Charlie

Explanation

a)

Object Alpha is a hoop of mass 55kg and radius 0.24m

Formula to use

I = (m)(r)(r)

I = 55(0.24)²

I = 3.168

Object Bravo is a disk of mass 86kg and radius .24m

Formula to use

I = 1/2(m)(r)(r)

I = 1/2(86)(0.24)²

I = 2.48

Object Charlie is a sphere of mass 112kg and radius .24m

Formula to use

I = 2/5(m)(r)(r)

I = 2/5(112)(0.24)²

I = 2.58

b)

As solid(sphere) object will always roll down the ramp faster than a hollow(disk, hoop) object of the same shape so Charlie will win the race down the incline plane

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