Classical Mechanics

Newton's Second Law Calculator

Solve F = ma for force, mass or acceleration. Also calculates weight.

Mass (m) — kg

Acceleration (a) — m/s²

Result

Weight on Earth

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Step-by-Step Solution

Newton's Second Law of Motion

Newton's Second Law states that the net force acting on an object is equal to its mass multiplied by its acceleration. It is the cornerstone of classical mechanics, connecting the cause (force) to the effect (acceleration) for any object with mass.

F = ma

F = net force (N) | m = mass (kg) | a = acceleration (m/s²)

Variables Explained

Symbol	Name	SI Unit	Description
F	Net Force	Newton (N)	The vector sum of all forces acting on the object
m	Mass	Kilogram (kg)	Measure of the object's inertia (resistance to acceleration)
a	Acceleration	m/s²	Rate of change of velocity — positive means speeding up

💡 The net force is the vector sum of all forces. If two equal and opposite forces act, F_net = 0 and the object does not accelerate (Newton's First Law).

Newton's Three Laws

First Law (Inertia): An object at rest stays at rest, and an object in motion stays in motion, unless acted on by an external force.

Second Law (F = ma): The acceleration of an object is directly proportional to the net force and inversely proportional to its mass.

Third Law (Action-Reaction): For every action there is an equal and opposite reaction.

Frequently Asked Questions

What is the difference between mass and weight?

Mass is the amount of matter in an object (kg) and does not change with location. Weight is the gravitational force on the object: W = mg. On the Moon, your mass is the same but your weight is 1/6th that on Earth.

Can F = ma be used for variable mass?

The basic form F = ma assumes constant mass. For variable-mass systems (like a rocket burning fuel), the more general form is F = dp/dt (rate of change of momentum), which reduces to F = ma when mass is constant.

What is a Newton?

One Newton is the force required to accelerate a 1 kg object at 1 m/s². It equals 1 kg·m/s². A typical apple weighs about 1 Newton (0.1 kg × 9.81 ≈ 1 N).