They both weigh the same but one is hollow, they rest on a flat surface with no other aids how do I tell which one is hollow
2007-11-09 08:15:44 · 14 answers · asked by Paddy 4 in Science & Mathematics ➔ Mathematics
They both weigh the same so magnets no good, they both sound the same so tapping's no good
2007-11-09 08:27:41 · update #1
they have different moments of inertia, so if you roll them, one will spin more rapidly than the other for the same initial velocity. but i forget which one. lol. maybe you should ask under physics.
2007-11-09 08:35:03 · answer #1 · answered by Michael M 7 · 3⤊ 0⤋
Let them roll from rest down an inclined plane.
For equal masses and equal radii the hollow sphere will have the greater moment of inertia and will have the lower acceleration.
Use
mgh = 1/2 mv^2 + 1/2 (M of I) w^2
w = v/r
mgh = 1/2 m v^2 + 1/2 (M of I) v^2/r^2
for the same mgh if (M of I) increases, v decreases.
For accel down the slope:
v^2 = u^2 + 2as
u=0
s the same in both cases
v decreases so a decreases.
2007-11-09 08:49:19 · answer #2 · answered by Red Campion 2 · 3⤊ 0⤋
Tap the surface close to the metal balls, rhe one with the dullest sound will be the full one and not the hollow one.
2007-11-09 08:22:47 · answer #3 · answered by ? 7 · 1⤊ 0⤋
Spin them,I believe the hollow one will keep spinning for longer.Alternatively let them both roll down a slope(both on the same slope.so tilt the board)the the one that gets to the bottom first will be solid.
2007-11-09 09:07:55 · answer #4 · answered by Anonymous · 3⤊ 0⤋
Snap each ball with your finger. The hollow one will give a hihger note.
2007-11-09 08:22:07 · answer #5 · answered by ironduke8159 7 · 0⤊ 0⤋
drop them from the same height the hollow one should bounce higher, if not increase the drop until one of them breaks
2007-11-09 08:24:46 · answer #6 · answered by Anonymous · 2⤊ 0⤋
Who cares which one is hollow. Just don't stand too close to the fire with your metal balls or you'll end up buring your inside leg.
2007-11-09 08:24:57 · answer #7 · answered by Anonymous · 0⤊ 2⤋
hold a big magnet above them, the one that isn;t hollow will hit the magnet first
2007-11-09 08:23:55 · answer #8 · answered by billybobjo 2 · 0⤊ 1⤋
do you know what metals they're made of? if you do, then there are books that give the densities of metals. the one with the higher density is the hollow one.
2007-11-09 08:21:23 · answer #9 · answered by sciencequeen 2 · 0⤊ 1⤋
roll them together the hollow one will ring.
2007-11-09 08:19:57 · answer #10 · answered by Anonymous · 0⤊ 0⤋