What is force?
Put simply, a force is something which changes the momentum of an object. The magnitude of a force is the rate of change of momentum caused.
This is shown by manipulation of the famous equation ##F=ma##
##F=ma=m(v_(f)-v_i)/t=(p_(f)-p_i)/t##
Where ##F## is the force
##m## is the mass of the object
##a## is acceleration, which is the rate of change of velocity
##v_i## is the initial velocity of the object which the force acts upon
##v_f## is the object’s final velocity
##t## is time
##p## is momentum, which is equal to ##mxxv##
Extra info:
Of course, because force is the rate of change of momentum, it can be linked to an object whose mass changes while velocity remains constant.
##F=(p_(f)-p_i)/t=v(m_(f)-m_i)/t##
Where ##m_f## is final mass and ##m_i## is initial mass.
Force can also be related to an object whose mass and velocity change simultaneously, but those equations involve calculus, so I won’t include those here.