Calculate force, mass, or acceleration using Newton's Second Law: F = ma.
Force is a push or pull that acts on an object. It is a vector quantity, meaning it has both magnitude and direction. In physics, force is measured in Newtons (N), named after Sir Isaac Newton. One Newton is defined as the force required to accelerate a 1 kg mass at 1 m/s².
Newton's Second Law states that the force acting on an object is equal to its mass multiplied by its acceleration (F = ma). This means a heavier object requires more force to accelerate at the same rate as a lighter object. It is one of the most fundamental principles in classical mechanics and is used in engineering, physics, and everyday problem solving.
| Unit | Symbol | Equivalent in Newtons |
|---|---|---|
| Newton | N | 1 N |
| Kilonewton | kN | 1,000 N |
| Pound-force | lbf | 4.44822 N |
| Dyne | dyn | 0.00001 N |
Mass is the amount of matter in an object and does not change regardless of location. Weight is the force exerted on an object due to gravity. On Earth, a 10 kg object weighs about 98 N (10 × 9.8 m/s²).
Earth's gravitational acceleration is approximately 9.8 m/s² (or 9.81 m/s² more precisely). This means any object in free fall accelerates downward at this rate, ignoring air resistance.
One Newton is roughly the force needed to hold a small apple — about 100 grams — against gravity. It gives you a practical sense of how much force 1 N actually represents.