Answer:

Explanation:
Given that
Mass of rifle = M
Initial velocity ,u= 0
Mass of bullet = m
velocity of bullet = v
Lets take final speed of the rifle is V
There is no any external force ,that is why linear momentum of the system will be conserve.
Initial linear momentum = Final linear momentum
M x 0 + m x 0 = M x V + m v
0 = M x V + m v

Negative sign indicates that ,the recoil velocity will be opposite to the direction of bullet velocity.
Answer:
P = 96 J
Explanation:
Given that,
Weight of the book, W = mg = 8 N
It is placed at a height of 12 m
We need to find the potential energy of the book. The potential energy of an object is given by the formula as follows :
E = mgh
mg = Weight

So, the potential energy of the book is 96 J.
By <span> It is directly proportional to the </span>average kinetic energy<span>.</span>