## Main Difference – Force vs. Power

**Force** and **power** are both quantities that come up in the study of mechanics. In everyday usage, the two terms may have similar connotations; however, in physics, the two terms have two separate meanings. The **main difference** between force and power is that the term force is used to describe something that can change the momentum of an object. In this sense, **force is defined as the rate of change of momentum**. **Power, on the other hand, refers to the rate at which a force is able to transfer energy**.

## What is Force

A force is something which has the ability to cause an object to change its momentum. Force is given by the rate of change of momentum:

Force is measured in units of **newtons** (N). A force of 1 N is about the weight of an apple.

Often, a force is described as a push or a pull. You need a force to change the motion of an object physically, like when you push a car. An electric circuit works because there is a force in the circuit that pushes electrons around the circuit. Forces are necessary to keep even small subatomic particles like protons and neutrons bound together in a nucleus. In larger scales, forces cause planets, stars and galaxies to attract each other via gravity.

## What is Power

**Work** is done whenever a force is used to move an object. Power is the rate of doing work. If the work done is , and time is given by then the power is given by:

Power is measured in **joules per second** (J s^{-1}) or **watts** (W). 1 W = 1 J s^{-1}.

Since Work done is given by , where is the displacement, we can write power as

Since the rate of change of displacement is the velocity , we can also express power in terms of the resultant force on an object and the object’s instantaneous velocity:

Power can also be defined as the **rate of energy transfer** when energy is transformed from one form to another. In a lightbulb, for example, the wattage refers to the rate at which the bulb can convert electrical energy to light.

Therefore, power is not just a measurement of how much force that an object can exert, but a measurement of the rate at which the force can do work.

## Difference Between Force and Power

### Definition of Force and Power

**Force** is something that can cause an object to change momentum.

**Power **is the rate of energy transfer.

### Nature of Quantity

**Force** is a vector quantity.

**Power** is a scalar quantity.

### Units

**Force** is measured in newtons (N).

**Power** is measured in watts (W).

**Image Courtesy**

“Like most machinery in Myanmar, our car was not in great shape…” by Roger Price from Hong Kong, Hong Kong (Uploaded by Fæ) [CC BY 2.0], via Wikimedia Commons