Question

Momentum of a body is defined to be the product of its mass and:
A. speed
B. velocity
C. acceleration
D. none of these

Answer 1

Momentum is a term that we hear used casually in everyday conversation. It is common to hear that sports teams and political candidates have "a lot of momentum." Momentum is a measure of mass in motion: how much mass is involved in how much motion.

Complete answer:
Linear momentum, translational momentum, or simply momentum (pl. momenta) is the product of an object's mass and velocity in Newtonian mechanics. It is a vector quantity with magnitude and direction. If an object's mass is $m$ and its velocity is $v$ (also a vector quantity), then its momentum is $p=m\times v$.

Momentum is measured in kilogram meters per second ($kgm/s$) in SI units. According to Newton's second law of motion, the rate of change of a body's momentum is equal to the net force acting on it. Momentum depends on the frame of reference, but it is a conserved quantity in any inertial frame, which means that if a closed system is not affected by external forces, its total linear momentum does not change.

Momentum is conserved in special relativity (with a modified formula), as well as in electrodynamics, quantum mechanics, quantum field theory, and general relativity (in a modified form). It is an expression of translational symmetry, which is one of the fundamental symmetries of space and time. So, Momentum is defined as the product of a particle's mass and velocity.

Thus, the answer is option B.

Note: Momentum is a vector quantity, which means that it has both magnitude and direction. Because momentum has a direction, it can be used to predict the resulting direction and speed of motion of colliding objects. The fundamental properties of momentum are described in one dimension below. Vector equations are nearly identical to scalar equations.