Force Calculator
Solve F = ma for force, mass or acceleration, and add several forces at different angles to find the net force and its direction.
Newton's second law
F = m × a
Solve for
F
Net force
N
2 sig figs: 3000
≡
Same value in
3,000,000 mN · 300,000,000 dyn · 674.4 lbf
- Rearrange: F = m × a
- Substitute: m = 1200 kg, a = 2.5 m/s² (converted to SI units first).
- Result: F = 3,000 N, rounded to 2 significant figures because the least precise input has 2.
Net force from several forces
Angles measured anticlockwise from the positive x-axis (0° = right, 90° = up).
ΣF
Net force
N
direction 45°
Fx Fy
Components
N
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0/1500
Worked example
A 1200 kg car accelerates at 2.5 m/s². The net force is F = 1200 × 2.5 = 3000 N. If the engine pushes with 3600 N, the other 600 N is going into air resistance and rolling friction.
Frequently asked questions
What is Newton's second law?
The net force on an object equals its mass times its acceleration: F = ma. Force in newtons, mass in kilograms, acceleration in m/s². 1 N is the force that accelerates 1 kg at 1 m/s².
What is net force?
The vector sum of all forces acting on an object. Forces in opposite directions subtract; forces at angles are added by components. Only the net force appears in F = ma.
How do I add forces at angles?
Resolve each force into x and y components (F cos θ, F sin θ), add all the x parts and all the y parts, then recombine: F_net = √(Fx² + Fy²), direction θ = arctan(Fy ÷ Fx). The net-force panel does this.
What is the difference between mass and weight?
Mass (kg) is how much matter; weight is the gravitational force on it, W = mg, in newtons. A 70 kg person weighs 687 N on Earth and 113 N on the Moon, with the same mass.