Relation of Speed Distance and Time

We will discuss here about the relation of Speed Distance and Time.

Speed is defined as the distance covered per unit time.

Speed = $\frac{\textrm{Distance Travelled}}{\textrm{Time Taken}}$

Or,

S = $\frac{D}{T}$

Speed also requires a unit of measurement. If the distance is in kilometers and the time is in hours, then the unit of measurement of speed is km per hour or km/hr.

For Example:

A car travels 120 km in 2 hours; find the speed of the car.

Speed = $\frac{120}{2}$

= 60 km/hr

Similarly, if the length is in metres and the time is in minutes, then the unit of measurement of speed is metre/per minute or m/min.

Average Speed

For Example:

1. A bus covers a distance of 325 kms in 5 hours. Find its average speed.

Solution:

Average Speed = $\frac{\textrm{Total Distance Covered}}{\textrm{Total Time Taken}}$

= $\frac{325 km}{5 hours}$

= 65 km/hr

2. A bus covers a distance of 420 kms in 6 hours. Find its average speed.

Solution:

Average Speed = $\frac{\textrm{Total Distance Covered}}{\textrm{Total Time Taken}}$

= $\frac{420 km}{6 hours}$

= 70 km/hr

3. Find the speed and average speed of a train which leaves the Florida Station at 10 p.m. and reaches next day at 10 a.m. The distance between the two stations is 648 km and the total time for stoppage is 2 hours between these stations.

Solution:

Total time taken = 10 p.m. to 10 a.m.

= 12 hours

Time for stoppage = 2 hours

Actual time taken = 12 hrs - 2 hrs = 10 hrs

Speed = $\frac{\textrm{Total Distance}}{\textrm{Actual Time Taken}}$

= $\frac{648 km}{10 hr}$

= $\frac{648}{10}$ km/hr

= 64.8 km/hr

Average Speed = $\frac{\textrm{Total Distance Covered}}{\textrm{Total Time Taken}}$

= $\frac{648}{12}$

(Including stoppage time) = 54 km/hr