watts = work per second.
work is mgh = 3x10x50=1500
watts out = 1500
Watts used = 2000
eff=1500/2000=75%
Answer:1.084
Explanation:
Given
mass of Pendulum M=10 kg
mass of bullet m=5.5 gm
velocity of bullet u
After collision let say velocity is v
conserving momentum we get


Conserving Energy for Pendulum
Kinetic Energy=Potential Energy

here
from diagram
therefore

initial velocity in terms of v

For first case 

for second case 

Therefore 


i.e.
The amplitude of the sound waves coming out of the speaker
or headphones will increase, and your little brother will start
banging on the wall and telling you to turn it down.