Newton's second law of motion

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Statement

In terms of force and acceleration

The net external force on a system is the product of the total mass of the system and the acceleration of its center of mass (here, mass is a scalar quantity and both force and acceleration are vector quantities). In symbols:

\overline{F} = m\overline{a}.

In particular, the direction of the net external force is the same as the direction of acceleration of the center of mass.

For a point mass or particle, we can talk of the acceleration of the whole body, and thus \overline{a} in the above refers to the acceleration of the point mass.

In terms of momentum and impulse

The net external impulse exerted on a system over a time period equals the difference between the final and initial values of its linear momentum. In other words, if the impulse from time t_1 to t_2 is I, the momentum at time t_1 is p_1, and the momentum at time t_2 is p_2, then:

I = p_2 - p_1.

External links

Instructional video links