Question

LGBARIDDLE!!!

You have two spheres. The outside dimensions, volume and mass are the same. The external part (the visible part) are made of the same material. The spheres are identical, no matter how you look at it. However, there is one piece of information that tells you they're different. One of the spheres is hollow. How do you determine which one is the hollow one?

(Hint: use physics concepts)

Answer 1

they make different noises ?

Answer 2

what do you mean by noises?

Answer 3

when you bang them with a hammer

Answer 4

seismic waves ...

Answer 5

rotate the two spheres...the hollow will stop 1st because it's moment of inertia is more than solid sphere..

Answer 6

the hollow sphere will make a better sound

Answer 7

i doubt either of those will work...since the external property of the balls will somehow bias your experiments. For example, even if you bang the balls, the outer covering will alter the sound produced, won't it?

Answer 8

why can't @akash123's method work? since the hollow sphere's mass will be concentrated at the border and the solid sphere's will be distributed uniformly, I will be more in the former case.
if we're applying same torque to both, angular acceleration for hollow < ang accel for solid. so the difference should be seen.

Answer 9

wait.. @akash123's method is about mass distribution of the sphere @Vaidehi09 ?

Answer 10

mass distribution will have an effect on moment of inertia right?

Answer 11

...i didn't know that...

Answer 12

but mass distribution is the right concept

Answer 13

oh good. so that's the answer.

Answer 14

yep

Answer 15

oh i know roll them down a hill

Answer 16

^right

Answer 17

and that's the correct experiment

Answer 18

which one wins , the shell?

Answer 19

shell?

Answer 20

hollow sphere = shell?

Answer 21

the hollow shell ball, as apposed to the solid sphere

Answer 22

the solid sphere will roll faster

Answer 23

the solid sphere should reach first ryt?

Answer 24

can you explain it

Answer 25

in my first answer...i explained why angular acceleration of solid sphere > angular accel of hollow sphere.
that should suffice?

Answer 26

the ball takes more energy for the same motion?

Answer 27

no. i don't think so. the potential energy for both at the top of the hill will be the same. so by the principle of conservation of energy, both will have the same energy at the bottom of the hill. the difference will be in the time taken to reach down.