1. A red billiard ball moving to the left -27 cm/s collides head on with a green
ID: 1319321 • Letter: 1
Question
1. A red billiard ball moving to the left -27 cm/s collides head on with a green ball moving to the right at 14 cm/s. The masses of the balls are identical. If the collision is perfectly elastic, what is the velocity of each ball after impact?
2.A m2 = 6 kg block of clay is suspended from the ceiling by a long cord, as seen in the following figure. A m1 = 230 gram bullet, fired horizontally, imbeds itself into the clay, causing both masses to rise to a height of 4.4 m. What is the velocity of the bullet?
3. A 4.6 kg ball travels from left to right at 8 m/s. A bat drives the ball in the opposite direction with a velocity of 18 m/s. If the time of contact was 0.14 seconds, what was the average force on the ball?
4.Two metal balls with equal masses are suspended, as shown in the following figure. If the ball on the right is lifted to a height of 2.8 feet and released to collide into the ball standing still, to what height will the resting ball rise? What velocity will the first ball collide into the standing still ball?
5.A car traveling at 28 m/s crashes into a truck with a mass of 9,300 kg stopped at a stoplight. What is the velocity of the wreckage immediately after the crash if the cars mass is 1,500 kg? (assume the truck and car stay together as one object)
Explanation / Answer
1) velocities will be interchanged.
Vr = +14 cm/s
Vb = -27 cm/s
2)
let v is speed of the bullet-blcok system after the bulled embeded in to the block.
so, h = v^2/2(2*g)
v = sqrt(2*g*h)
= sqrt(2*9.8*4.4)
= 9.286 m/s
Apply conservation of momentum
m1*u1 = (m1+m2)*v
u1 = (m1+m2)*v/m1
= (0.23+6)*9.286/0.23
= 251.5 m/s
3) Apply, impulse = chnage in momentum
F*dt = m*(v2-v1)
F = m*(v2-v1)/dt
= 4.6*(-8-18)/0.14
= -854.3 N
4) h = 2.8 feet
velocity of first ball = 0
5) Apply
m1*u1 = (m1+m2)*v
v = m1*u1/(m1+m2)
= 1500*28/(1500+9300)
= 3.8 m/s
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