1. Abbey and Mia are in the basement playing pool. On Abbey\'s recent shot, the
ID: 249589 • Letter: 1
Question
1. Abbey and Mia are in the basement playing pool. On Abbey's recent shot, the cue ball was moving east at 82 cm/s when it struck the slower 5-ball of identical mass moving in the same direction at 24 cm/s. The 5-ball immediately speeds up to 52 cm/s. Determine the post-collision speed of the cue ball in cm/s.
2. A 2.0 g bullet, moving at 538 m/s, strikes a 0.25 kg piece of wood at rest on a frictionless table. The bullet sticks in the wood, and the combined mass moves slowly down the table. Find the speed of the two after the collision in m/s.
3. In the previous problem, How much of the original kinetic energy, in joules, was lost during the collision?
4. Bullets bounce from superman’s chest. Suppose that superman, with a mass of 104 kg while not moving is struck by a 4.2 g bullet moving with a speed of 835 m/s. The bullet drops straight down with no horizontal velocity. How fast would superman move after the collision if his superfeet were frictionless. (Give your answer in m/s, and round to the nearest .001) *
Explanation / Answer
1) let u1 = initial speed of cue ball = 82 cm/s
u2 = initial speed of 5 balls = 24 cm/s
V1 = final speed ( speed after collision) of cue ball = ?
V2 = final speed of 5 balls = 52 cm/s
from conservation of momentum :
initial momentum = final momentum
m1*u1 + m2*u2 = m1*V1 + m2*V2
let all balls ( cue and 5 balls) are of same mass ie m1 = m2 = m
so m*( u1+u2) = m( V1+V2)
u1+u2 = V1+ V2
V1 = u1+u2 - V2
= 82 +24 - 52
= 54 cm/s
2) let m1 = mass of ball = 2*10-3kg
u1 = initia velocity of ball = 538 m/s
m2 = mass of wood = 0.25 kg
u2 = initial speed of wood = 0m/s due to at rest
V = final speed of wood + ball = ?
from conservation of momentum :
initial momentum = final momentum
m1*u1 + m2*u2 = (m1+ m2 )*V
2*10-3538 + 0.25*0 = ( 2*10-3 + 0.25)*V
V = 4.269 m/s
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