Answer:
D. Friction
Explanation:
Friction is a force that opposes motion. So a perpetual motion machine can never be built because it is impossible to eliminate frictional force. It can only be reduced
Answer:

Explanation:
Given that,
The mass of the paperclip, m = 1.8 g = 0.0018 kg
We need to find the energy obtained. The relation between mass and energy is given by :

Where
c is the speed of light
So,

So, the energy obtained is
.
Answer:
5.959 m/s
Explanation:
m = Mass of gymnast
u = Initial velocity
v = Final velocity
= Initial height
= Final height
From conservation of Energy



Velocity of gymnast at bottom of swing is 5.959 m/s
Answer:
the size, length, or amount of something, as established by measuring.
This is a concave mirror you're talking about, so all of the points are going to converge to a single focal point. Therefore the answer would be that it bounces back toward a single spot