Force Calculator
Solve for force, mass, or acceleration using Newton's Second Law (F = ma)
Solve For
Solve for Force (F = ma)
Mass (m)
kg
Acceleration (a)
m/s²
Force (F)
N
Newton's Laws
F = m × a
m = F / a
a = F / m
W = m × g
Results
Force
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Mass
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Acceleration
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Newton's Second Law
Newton's Second Law states that the net force acting on an object equals its mass times acceleration (F = ma). Force is measured in Newtons (N), where 1 N = 1 kg·m/s². Weight is a special case: the gravitational force on an object (W = mg).
On Earth, g = 9.81 m/s². A 70 kg person weighs 686.7 N (about 154.5 lbf). On the Moon (g = 1.62 m/s²), the same person weighs only 113.4 N. Mass is constant everywhere; weight changes with gravity.
lightbulb Example
Push a 5 kg box with 20 N force:
1F = 20 N, m = 5 kg
2a = F/m = 20/5 = 4 m/s²
✓ Box accelerates at 4 m/s²
quizFrequently Asked Questions
What is the difference between mass and weight?
Mass is the amount of matter in an object (measured in kg, constant everywhere). Weight is the gravitational force on that mass (F = mg, measured in Newtons). On Earth, g ≈ 9.81 m/s², so a 10 kg object weighs ~98.1 N. On the Moon (g ≈ 1.62 m/s²), the same mass weighs only ~16.2 N — about one-sixth of its Earth weight.
What is Newton's Second Law?
F = ma. Force (in Newtons) equals mass (in kg) multiplied by acceleration (in m/s²). A 1 Newton force accelerates a 1 kg mass at 1 m/s². To accelerate a 1000 kg car from 0 to 100 km/h in 10 seconds requires approximately 2,778 N of net force — ignoring friction and air resistance.
What are the common types of force in engineering?
Tensile force (pulling, like a rope under load), compressive force (pushing, like a column bearing weight), shear force (parallel to a surface, like scissors cutting), torsional force (twisting), and bending moment (force × distance). Understanding these forces is essential for structural engineering, machine design, and material selection.