Answer:
Explanation:
Kinetic energy of ball
= .5 x .5 x 20²
= 100 J
Original kinetic energy of door = 0
Total kinetic energy before ball hitting the door
= 100 J
We shall apply law of conservation of momentum to calculate angular velocity of the door after ball hitting it.
change in angular momentum of ball
= mvr - mur , u is initial velocity and v is final velocity of ball
= .5 ( 20 + 16 ) x .06
= 1.08
Change in angular momentum of door
= I x ω - 0
1/3 x 35 x .09² x ω
= .0945 x ω
so
.0945 x ω = 1.08
ω = 11.43
rotational K E of door after collision
= 1/2 I ω²
= .5 x .0945 x 11.43 ²
= 6.17 J
Kinetic energy of ball after collision
= 1/2 x .5 x 16²
= 64
Total KE of door and ball
= 64 + 6.17
= 70.17 J
LOSS OF ENERGY
= 100 - 70.17 J
= 29.83 J
