.

Thereof, how can speed be calculated?

Divide the distance by the time to find the speed. All you need are these two pieces of information to find your speed for the trip. The distance over the time will give you the object's speed. In our example, 100 miles/2 hours = 50 miles/hour (about 80 kilometers/hour).

Subsequently, question is, how do we measure light speed? The speed of light in a vacuum stands at “exactly 299,792,458 metres per second“. The reason today we can put an exact figure on it is because the speed of light in a vacuum is a universal constant that has been measured with lasers; and when an experiment involves lasers, it's hard to argue with the results.

what is used to measure speed?

Speed measuring instruments vary with the job. Whether measuring traveling speed, wind speed, acceleration or engine speed, there is a proper instrument for calculating that form of speed. Police use RADAR and LIDAR to measure traffic speed. Accelerometers are also used with car speed measurements.

What is constant speed?

constant speed means that there is no acceleration. For example a car moving at 50 mph is going at a constant speed, but a car that is standing still on the road and speeds up to 50 pmh is in a constant state of acceleration. Once the car reaches 50 mph there is zero acceleration and you are moving at a constant speed.