The answer would be option D "a ball sitting on a shelf." Potential energy is the amount of energy a object has while it's at rest.. (or not moving) Kinetic energy is how much energy a object is while it's moving. So in this case it's option D because a ball sitting on a shelf isn't moving therefore it has potential energy. It's not option A because thats a example of kinetic energy since how the roller coaster is moving. It's not option B because it's kinetic energy because the bike is moving. It's also not option C because it's kinetic energy because the bird is moving.
Hope this helps!
Jupiter Cannot Become A Star.
Jupiter Is The Fastest Spinning Planet In The Solar System.
The Clouds On Jupiter Are Only 50 km Thick.
Answer:-q
Explanation:
Given
Capacitor is charged to a battery and capacitor acquired a charge of q i.e.
+q on Positive Plate and -q on negative Plate.
If the plate area is doubled and the plate separation is reduced to half its initial separation then capacitor becomes four times of initial value because capacitor is given by

where A=area of capacitor plate
d=Separation between plates
This change in capacitance changes the Potential such that new charge on the negative plate will remain same -q
So the best conductor for electricity is silver.
However because silver is so expensive we use copper which is the next best conductor
Answer:
A lone neutron spontaneously decays into a proton plus an electron.
Explanation:
In an atom, nuclei contain protons and neutrons, which are the fundamental particles of an atom. Neutrons are stable and uncharged particles inside a nucleus.
For 15 times during its lifetime, a free neutron decays and breaks down into more smaller particles.This breakdown causes problems in nuclear reactors, as they start decaying and emit radiations of different wavelengths.
A neutron undergoes the decaying process to produce an electron, a proton, and energy.
The reaction of neutron decay:
n0 → p+ + e− + νe