The grinch has already started to dread the christmas season. \"There\'s one thi
ID: 1775490 • Letter: T
Question
The grinch has already started to dread the christmas season. "There's one thing I hate ... all the noise, noise, noise," grimaces the grinch.
He is particularly tormented every year by the wailing of a "Who-whooper" by little Cindy Lou Who, so the grinch decides to take matters into his own hands.
The grinch takes a gun, stalks his way down to Whoville to Cindy Lou Who's window with a crazed look in his eye, takes aim, and fires a 12 g bullet into the target: a 1.2 kg "Who-whooper" that starts at rest on a frictionless surface.
The bullet passes right through it and emerges on the other side with a speed of 100 m/s, and the "Who-whooper" is given a speed of 4 m/s as a result of the collision.
Find the initial speed of the bullet.
m/s
Find the amount of energy dissipated as heat in its trip through the "who-whooper."
J
Explanation / Answer
Using law of conservation of momentum
momentum before collision = momentum after collision
(12*10^-3*u1)+(1.2*0) = (12*10^-3*100)+(1.2*4)
u1 = 500 m/sec is the initial speed of the bullet
amout of energy dissipated as heat is Kf-Ki
Ki = (0.5*12*10^-3*500^2) = 1500 J
Kf = (0.5*12*10^-3*100^2)+(0.5*1.2*4^2) = 69.6 J
so amout of energy dissipated as heat is Kf-Ki = 69.6-1500 = -1430.4 J
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