Impulse and moment of force
Impulse means change in the momentum of a body i.e. Impulse = Ft = mv - mu The turning effect of force about the axis of rotation is called moment of force or torque. So they don't have any units... resulting no dimensions!!
momentum
1)According to newton,s 2nd law force = rate of change of momentum i.e.,momentum=m*v F= M*(D*V/DT)=M*A so it is case of m1v1 and m2v2 m1 is not = m2 hence v1 is not = v2 now Newton's 3rd law come in pictutre during impact F1=F2 ......(equal and opposite reaction) hence m1a1=m2a2 momentum1=momentum2 2)it can be a case of special relativity increase in velocity= increase in inertia = increase in enrgy then apply law of conservation of energy again newtons 3rd law 3)concider it is case of closed system between two bodies
pressure
A scalar quantity is defined as the physical quantity that has only magnitude, for example, mass and electric charge. Pressure has only magnitude and not definite direction, hence pressure is a scalar quantity.
On the other hand, a vector quantity is defined as the physical quantity that has both magnitude as well as direction like force, weight, acceleration and velocity.
Alternating current to Direct current
Because in rectifier circuit there will be a diode in which the current flows in forward bias only when we apply alternating current so it is a unidirectional current of ripples so it is used to covert ac to dc.
neutrons
Neutron reside in the nucleus of the atom and it is heavy than other elementary particles hence it is imposssible to have a emission of neutron.