Answer:
Newton's third law, if i'm not mistaken.
Explanation:
Any action that occurs will have a opposite and equal action. The greater the force u apply to the wall, the greater the force the wall exerts back at you, hence why ur hands become red if u try pushing extremely hard on the wall.
The acceleration of the bike is 
Explanation:
We can solve this problem by using Newton's second law of motion, which states that:
where
F is the net force on an object
m is the mass of the object
a is its acceleration
For the bike in this problem, we have
F = 175 N is the net force
m = 50 kg is the mass
And solving for a, we find the acceleration:
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The electric potential difference is the electric potential energy per unit charge
Explanation:
First of all, we define the concept of electric potential. The electric potential is a measure of the gradient of the electric field at a certain point of the space. The electric potential at a distance 
from a positive charge of magnitude 
is given by
where k is the Coulomb's constant.
Now we can define the electric potential energy and the electric potential difference:
- Electric potential energy is the energy possessed by a charge due to the presence of an electric field. For a charge of magnitude immersed in an electric field, its potential energy is given by
, where V is the electric potential at the location of the charge. - The electric potential difference is simply the difference in electric potential between two points in the space. For instance, if the potential at point A is V(A) and the potential at point B is V(B), then the potential difference is
The electric potential energy is also defined as the work done on a charge q moved through a potential difference of 
. Consequently, the potential difference represents the work per unit charge done, i.e. the work done when moving a unitary charge through a potential difference .
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Answer:
Pu - 239 have the smaller critical mass.
Explanation:
Critical mass is the smallest amount of certain element of mass that is needed to achieve a nuclear chain reaction early . Since Pu - 239 releases an average of 2.7 neutrons per fission as compared to U - 235 that releases 2.5 neutrons per fission. So, Pu - 239 has smaller critical mass, because Pu - 239 has a higher probability for fission and produces a large no. of neutrons per fission event. Infact of all the basic nuclear fuels, Pu - 239 has smallest critical mass. Critical mass depends on the nuclear properties of elements undergoing fission reaction. Hence, as Pu - 239 produces large no. of neutrons per fission than U - 235 and Pu - 239 has smaller critical mass.
Explanation:
unit is necessary to communicate values of the physical quantity for example can main to someone a particular length without using some sort of unit is impossible because a length cannot be described without a reference used to make sense of the value given
