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What is Force in Physics?

Force is an interaction that causes a change in the motion of an object. According to Newton's Second Law, force equals mass times acceleration (F = m × a). Force is measured in Newtons (N), where 1 Newton is the force needed to accelerate a 1 kg mass by 1 m/s². The concept of force is fundamental in mechanics physics and has broad applications in engineering, construction, and everyday life.

Newton's Second Law

F = m × aFormula: a = F/m or m = F/a

Variables:

  • FForce in Newtons (N)
    Force in Newtons (N)(e.g.: F = 100 N)
  • mMass in kilograms (kg)
    Mass in kilograms (kg)(e.g.: m = 10 kg)
  • aAcceleration in m/s²
    Acceleration in m/s²(e.g.: a = 10 m/s²)
  • WWeight (gravitational force) = m × g
    Weight (gravitational force) = m × g(e.g.: W = m × 9.8 N)

Categories:

Newton's First LawObjects stay at rest/uniform motion without force
Newton's Second LawF = m × a
Newton's Third LawAction = Reaction

How to Use the Force Calculator

  1. 1

    Choose the Unknown Variable

    Select whether you want to find force (F), mass (m), or acceleration (a).

  2. 2

    Enter Values

    Enter the two known values.

  3. 3

    Calculate

    The system will compute the unknown variable.

  4. 4

    View Results

    Results are displayed with the appropriate units.

Examples

Accelerating Car

Problem:

A 1000 kg car accelerates at 2 m/s². What force is required?

Solution:
  1. 1.F = m × a
  2. 2.F = 1000 × 2 = 2000 N
Result:2000 N (2 kN)

A force of 2000 Newtons is required to accelerate the car.

Body Weight

Problem:

What is the weight of a 70 kg person on Earth (g = 9.8 m/s²)?

Solution:
  1. 1.W = m × g
  2. 2.W = 70 × 9.8 = 686 N
Result:686 N

Weight is the gravitational force acting on mass.

Frequently Asked Questions

What is the difference between mass and weight?
Mass is the amount of matter (constant everywhere, unit kg). Weight is the gravitational force on mass (varies by location, unit N). On the Moon, your weight is about 1/6 of your weight on Earth.
What is net force?
Net force is the vector sum of all forces. Forces in the same direction add; opposing forces subtract. An object accelerates when net force ≠ 0.
Why is 1 N defined this way?
1 Newton is the force needed to give a 1 kg mass an acceleration of 1 m/s². This definition makes calculations straightforward in the SI system.

Related Calculators

Acceleration

Uniform motion and kinematics

Momentum

p = m × v

Work & Power

W = F × s

References