CalculateY
Quick Answer
A 10 kg object accelerating at 9.8 m/s^2 experiences a net force of 98.00 N. The weight of a 75 kg person on Earth is 735.75 N.
Newton's Second Law (F = ma)
Weight from Mass (W = mg)
Earth: 9.81, Moon: 1.62, Mars: 3.72, Jupiter: 24.79
Common Examples
| Input | Result |
|---|---|
| m = 10 kg, a = 9.8 m/s^2 | F = 98.00 N |
| F = 500 N, m = 50 kg | a = 10.00 m/s^2 |
| F = 200 N, a = 4 m/s^2 | m = 50.00 kg |
| m = 75 kg, g = 9.81 m/s^2 (weight) | W = 735.75 N |
| m = 75 kg, g = 1.62 m/s^2 (Moon) | W = 121.50 N |
How It Works
This calculator uses Newton’s Second Law of Motion:
F = m x a
Where:
- F = net force in Newtons (N)
- m = mass in kilograms (kg)
- a = acceleration in meters per second squared (m/s^2)
One Newton is defined as the force required to accelerate a one-kilogram mass at one meter per second squared. The equation can be rearranged:
- Force: F = m x a
- Mass: m = F / a
- Acceleration: a = F / m
Weight as a Force
Weight is the gravitational force acting on an object:
W = m x g
Where g is the gravitational acceleration. On Earth’s surface, g = 9.81 m/s^2. Weight is measured in Newtons, not kilograms. A 1 kg mass weighs 9.81 N on Earth but only 1.62 N on the Moon, because the Moon’s gravitational acceleration is smaller.
Force Units
- 1 Newton (N) = 1 kg x m/s^2
- 1 kilonewton (kN) = 1,000 N
- 1 pound-force (lbf) = 4.44822 N
- 1 dyne = 0.00001 N
Net Force and Multiple Forces
Newton’s second law applies to the net (total) force on an object. If multiple forces act on an object, the acceleration depends on the vector sum of all forces. This calculator assumes you are entering the net force or solving for it directly.
Worked Example
A 1,200 kg car accelerates at 2.5 m/s^2. The net force is F = 1,200 x 2.5 = 3,000 N (3 kN). Conversely, if a 50 N force acts on a 10 kg box, the acceleration is a = 50 / 10 = 5.0 m/s^2. For weight: a 75 kg person on Earth weighs W = 75 x 9.81 = 735.75 N. On Mars (g = 3.72 m/s^2), the same person weighs W = 75 x 3.72 = 279.00 N.