Name: Relative Motion and Frame of Reference
Uploaded: 2019-07-19
Duration: 6 min 27 s
Description: Are you moving right now? It depends upon which frame you are in and from which frame you are observing. Explore relative motion and reference frames.

Question

State Newton's second law of motion. How does it help to measure force? Define S.I. unit of force.

Accepted Answer

Newton's second law of motion states that the rate of change of momentum of a body is directly proportional to the applied force and takes place in a direction in which the force acts.

Expression for force can be obtained using the second law of motion. We know that the momentum of a body is defined as the product of the mass and the velocity of a body. Hence, if the velocity of a body of mass $m$ changes from $v$ to $v + ∆ v$ in a time interval of $∆ t$ then, change in its momentum $(∆ p)$ :

$∆ p = m ∆ v$

According to Newton's second law of motion:

$F \propto \frac{∆ p}{∆ t}$

$\Rightarrow F = k \frac{∆ p}{∆ t}$

$For k = 1$

$F = \frac{∆ p}{∆ t} = \frac{m ∆ v}{∆ t} = m a$

Hence, if the acceleration and the mass of a body is known then the force applied on the body can be calculated using the above formula for the force. The SI unit of force is newton. One newton is the amount of force that causes an acceleration of $1 m s^{- 2}$ when applied to a body of mass equal to $1 kg$ .

State Newton's second law of motion. How does it help to measure force? Define S.I. unit of force.

Important Questions on Force : Newton's Laws of Motion

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