A 100 g ball moving to the right at 4.4 m/s catches up and collides with a 450 g

Question

A 100 g ball moving to the right at 4.4 m/s catches up and collides with a 450 g ball that is moving to the right at 1.2 m/s .

Part A

If the collision is perfectly elastic, what is the speed of the 100 g ball after the collision?

Express your answer to two significant figures and include the appropriate units.

m/s

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Part B

If the collision is perfectly elastic, what is the direction of motion of the 100 g ball after the collision?

If the collision is perfectly elastic, what is the direction of motion of the 100  ball after the collision?

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Part C

If the collision is perfectly elastic, what is the speed of the 450 g ball after the collision?

Express your answer to two significant figures and include the appropriate units.

m/s

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Part D

If the collision is perfectly elastic, what is the direction of motion of the 450 g ball after the collision?

If the collision is perfectly elastic, what is the direction of motion of the 450  ball after the collision?

m/s

Explanation / Answer

A)
use conservation of momentum,
m1*v1i + m2*v2i = m1*v1f + m2*v2f
100*4.4 + 450*1.2 = 100*v1f + 450*v2f
100*v1f + 450*v2f = 980
v1f = (980 - 450*v2f)/(100)
= 9.8 - 4.5*v2f

for elastic collision
e = -1
e = (v2f-v1f) / (v2i - v1i)
-1 = (v2f - 9.8 + 4.5*v2f) / (1.2-4.4)
3.2= 5.5 v2f - 9.8
v2f = 2.4 m/s

v1f = 9.8 - 4.5*v2f
= 9.8 - 4.5 * 2.4
= -1 m/s

Answer: 1.0 m/s

B)
negative sign in v1f shows that it is towards left
Answer: To the left

C)
v2f = 2.4 m/s
Answer: 2.4 m/s

D)
Answer:
to the right

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