What is Force? | Definition, Types, Formula & Examples

What is Force?

In physics, a force is an action that pushes or pulls an object. A force can cause an object to speed up, slow down, stay in place, or change shape.

How to Measure Force

The unit of force is the newton, abbreviated as “N”. One newton is the force required to accelerate one kilogram of mass by one meter per second squared (N = 1 kg m/s2). Other units of force include dyne and pound-force.

Force, Mass, and Acceleration

Force can be determined if you know the mass and acceleration of an object. This equation comes from Newton’s second law of motion:

f = m * a

Where f = force, m = mass, and a = acceleration.

Forces and Vectors

The force has not only magnitude (which we calculate in newtons using the above equation), but also direction. This makes the force a vector. Vectors are represented by an arrow indicating the direction of the force and a number indicating the magnitude. See the figures to the right for how to use arrows to indicate the direction of force.

Forces in Equilibrium

Sometimes multiple forces can be applied to an object but the object remains at rest. In this case, the forces are balanced. The sum of the forces, or net force, is zero.

Combined Forces

When several forces are applied to an object, the resulting force is the sum of the vectors of the individual forces. We won’t go into complicated vector math here, but let’s take the hand object as an example. Both sides shot each other. If one side pulls with a force of 2 N in the left direction and the other pulls with a force of 3 N in the right direction, the resulting force is 1 N in the right direction.

Types of Forces

Friction – Friction is the force produced when one object rubs against another. It works in the opposite direction to the main force.

Gravity – Gravity – Gravity is a force exerted by a large body, such as the Earth. Gravity pulls objects towards Earth with an acceleration “g” equivalent to 9.8 m/s2.

Electromagnetic – Electromagnetic force is the force that has the effect of electric and magnetic fields.

Nuclear – The nuclear force is the force that holds atoms and their particles together.

Tension – The force exerted by a rope, cable or chain on another object.

Elastic – Elastic force is the force exerted by an object when trying to return to its natural length. This is modeled by a spring that has been pulled by an external force, but pulled back while trying to return to its original length.

Interesting Facts about Force

An object accelerating in circular motion experiences a “radial” force.

The four fundamental forces are gravity, electromagnetism, the strong nuclear force, and the weak nuclear force.

Torque is a type of force that measures the change in the rotational speed of an object. Torque is an important characteristic of cars, especially trucks.

Resistance is the force that reduces the speed of an object. Thrust is the force that increases the speed of an object.