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Newton's second law

Newton's second law links the forces acting on a body to the acceleration it gets. The sum of all forces, found from a free-body diagram, equals mass times acceleration. The law applies in each direction separately.

\sum F = ma

Newton's second law

Symbols

$F$	force	N
$m$	mass	kg
$a$	acceleration	m/s²

Example

A 5 kg block is pulled with 30 N, with 10 N friction against it:

$a = (30-10)/5 = 4$ m/s².

Constant speed means

\sum F = 0

, not that a force is needed to keep the speed up.

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Part of Statics and Dynamics: Dynamics.