Force Calculator — Newton’s Second Law F = ma
Newton’s second law, F = ma, is the workhorse of mechanics: the resultant force on an object equals its mass multiplied by its acceleration. Enter any two of the three quantities and this calculator finds the third.
Remember that F is the resultant (net) force. If several forces act, they must be added as vectors first — friction and driving force in opposite directions partly cancel.
Use the calculator
Enter any TWO values — the calculator solves the third.
The formula
F = ma — so a = F / m and m = F / a. One newton is the force that accelerates 1 kg at 1 m/s².
Worked example
Worked example: A 1,200 kg car accelerates at 2.5 m/s². The resultant force needed is F = ma = 1,200 × 2.5 = 3,000 N.
Frequently asked questions
What is a newton in simple terms?
One newton (1 N) is the resultant force that gives a mass of 1 kg an acceleration of 1 m/s². It is roughly the weight of a small apple (about 100 g) on Earth.
Is F = ma the same as weight?
No. Weight is one specific force: the gravitational pull on a mass, W = mg. F = ma applies to any resultant force, of which weight is just one example.
Why does a heavier car need more force to accelerate?
Because acceleration equals force divided by mass (a = F/m). For the same acceleration, doubling the mass doubles the force required.