In physics, speed is defined as the rate at which an object changes its position. It is a scalar quantity, meaning it only has magnitude and no direction. Speed is typically measured in meters per second (m/s) or kilometers per hour (km/h).

Here's a more formal definition:

Speed is the distance traveled by an object per unit of time.

Mathematically, this can be expressed as:

Speed = Distance / Time

For example, if a car travels 100 kilometers in 2 hours, its average speed is:

Speed = 100 km / 2 hours = 50 km/h

It's important to note that this is the average speed over the entire journey. The car might have traveled at different speeds during those two hours, but the average speed is the total distance divided by the total time.

Instantaneous speed is the speed of an object at a specific point in time. This can be measured using devices like a speedometer.

Key points to remember about speed:

* It is a scalar quantity.

* It is always positive.

* It is measured in units of distance per unit of time.

* Average speed is the total distance traveled divided by the total time taken.

* Instantaneous speed is the speed at a specific moment in time.