Question

1-From a top-down view of a pool table, a white billiard ball is shot at 1.2 m/s directly to the right into a green billiard ball. If the white ball collides and ricochets directly upwards at 0.5 m/s, how fast does the green billiard ball go after getting hit? (in meters per second)

2- A 20-gram bullet is fired at 800 m/s at a free-standing 780-gram wood block on a table. When the bullet embeds itself in the wood, the whole piece is knocked back at a speed of _______ m/s.

Answer 1

1. Given :

initial velocity of white ball =

final velocity f white ball =

Let the velocity of green ball be = .

Mass of all the balls is same.

Now, applying conservation of linear momentum of system :

The magnitude of vecocity of grren ball is [answer]

2) given :

m = mass of bullet = 20 g

M = mass of wooden block = 780 g

u = inital velocity of bullet = 800 m/s

After collision they stick to each other.

Let the speed of the system after collision be v

Applying conservation of linear momentum :

(M+m) v = m*u

=> (780+20) v = 20*800

=> v = 20 m/s [answer]