Mechanical · Newton's Laws

Newton's Second Law — F = ma

Push on a mass and it accelerates. The bigger the force the faster it speeds up; the heavier the object the more sluggishly it responds. Acceleration is force divided by mass.

Controls

a = F/m = 5.0 m/s²
Acceleration a5.00 m/s²
Velocity v0.0 m/s
Position x0.0 m
Elapsed time0.0 s
Force on → it accelerates.
About this experiment ›

What you are looking at

A block sits on a frictionless surface. While the force is on (the gold arrow), the block accelerates — its velocity climbs steadily, traced on the graph. Turn the force off and the velocity stays flat: with no net force the block coasts (that's the first law). Turn it back on and it speeds up again.

The second law

Newton's second law ties force, mass and acceleration together:
F = m a  ⟺  a = F / m
Acceleration is how fast velocity changes. For a given mass, double the force and you double the acceleration. For a given force, double the mass and you halve the acceleration — heavier things are harder to get moving, which is exactly what "mass" means (inertia). Watch the a = F/m readout update as you drag the sliders, and notice the slope of the velocity graph (which is the acceleration) change to match.

Velocity and position

Under constant acceleration from rest, velocity grows linearly, v = at, and distance grows as the square of time, x = ½at². That straight velocity line and the ever-steeper position are the fingerprints of a constant net force.

Things to try

Set a force and mass, watch the slope; double the force and see the line get twice as steep; double the mass and see it go half as steep. Set the force to zero (or toggle it off mid-run) to watch the block obey the first law and coast at whatever speed it had reached.