Question

What is momentum? Write its SI unit. Interpret force in terms of momentum.

Answer 1

Hint: Momentum of a body is defined as the product of the mass and the velocity of the body. Momentum is a vector quantity, which means that it has a magnitude as well as direction. You can use the definition to find the unit of momentum.

Complete answer:
When a body is in motion, we change that it possesses some momentum. Momentum of a body is defined as the product of the mass and the velocity of the body. When we talk about momentum of a body, we are concerned with its direction. Its direction is along the direction of the velocity of the body. Therefore, momentum is a vector quantity.

If a body of mass m is moving with a velocity $\overrightarrow{v}$, then its momentum is equal to $\overrightarrow{P}=m\overrightarrow{v}$. The magnitude of the momentum is equal to $P=mv$. Since momentum is a product of the mass and velocity, its unit is the product of units of mass and the velocity. Therefore, the unit of momentum is $kgm{{s}^{-1}}$.

Now, the rate of change in the momentum of a body is defined to be the force exerted on the body.Therefore, the applied force is written as, $\overrightarrow{F}=\dfrac{d\overrightarrow{P}}{dt}$.
Force is a vector quantity. The direction of the applied force on a body is in the direction of the change in momentum. The SI unit of force is Newton (N). And $1N=1kgm{{s}^{-2}}$

Note: When the momentum of a body changes uniformly with time, then the force is constant. If in a time interval $\Delta t$, the change in the momentum is equal to $\Delta P$, then the magnitude of the force is equal to $F=\dfrac{\Delta P}{\Delta t}$.