Forces: Calculating Forces

Forces: Calculating Forces

Calculating Forces


  • A force can be thought of as a push or a pull on an object. Forces can cause an object to start or stop moving, or to change its motion.

  • Force is a vector quantity, meaning it has both magnitude (size) and direction.

  • The unit of force in the International System of Units (SI) is the newton (N).

Resultant Force

  • If more than one force acts on an object along the same line, the forces can be added or subtracted to find the resultant force.

  • In other words, the resultant force is the total force resulting from the combination of all the individual forces acting on an object.

  • If the forces acting on an object are balanced, the resultant force is zero and the object stays at rest or continues moving at the same speed in the same direction.

  • If the forces are unbalanced, the resultant force is not zero and the object accelerates in the direction of the resultant force.

Calculating Force

  • The formula for calculating force is Force (N) = mass (kg) x acceleration (m/s²). This relation is known as Newton’s second law of motion.

  • If an object is not accelerating, the force applied to it is balanced by the force of friction or any other opposing force. So, the net force or the resultant force is zero.

  • In case of an unbalanced force, the object will accelerate in the direction of the resultant force. This acceleration can be calculated by rearranging the formula: acceleration (m/s²) = Force (N) / mass (kg).


  • Friction is a force that opposes motion. It acts parallel to the surfaces in contact and opposite to the direction of motion.

  • The roughness of the surfaces and the force pushing them together determine the amount of friction.

  • While calculating forces, if an object is moving and experiencing some friction, it’s important to take this force into account.

  • In some scenarios, to decrease friction, lubricants are used whereas, in some cases, like braking of vehicles, increasing friction is beneficial.