 #1
asifion
 18
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 Homework Statement:
 A mad engineer builds a cube, 2.5 m on a side, in which 6.2cmdiameter rubber balls are constantly sent flying in random directions by vibrating walls. He will award a prize to anyone who can figure out how many balls are in the cube without entering it or taking out any of the balls. You decide to shoot 6.2cmdiameter plastic balls into the cube, through a small hole, to see how far they get before colliding with a rubber ball. After many shots, you find they travel an average distance of 2.8 m. How many rubber balls do you think are in the cube?
 Relevant Equations:

not sure but: N/V=p/(k_B*T)
pV=nRT
V/N = distance between atoms?
So, I was thinking that the total volume of the cube divided by the number of atoms (or rubber balls) should intuitively give the average distance between each ball.
What I did was:
N = number of balls
D = avg distance between balls
(2.5)^3 / N = D
(2.5)^3 / D = N
D = 2.8  2 * radius (I'm assuming the given average distance is from center to center of each sphere)
2.5^3/(2.8.062) = 5.7 balls
What I did was:
N = number of balls
D = avg distance between balls
(2.5)^3 / N = D
(2.5)^3 / D = N
D = 2.8  2 * radius (I'm assuming the given average distance is from center to center of each sphere)
2.5^3/(2.8.062) = 5.7 balls
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