Question

A train takes 2 ja to reach station B from station A,
and then 3 h to return from station B to station A.
The distance between the two stations is 200 km.
Find : (i) the average speed, (ii) the average
velocity of the train.​

Answer 1

Answer

Average Speed of the train = 80 Km/h

Average Velocity of the train = 0 Km/h

Given

A train takes 2 h to reach station B from station A,  and then 3 h to return from station B to station A.  The distance between the two stations is 200 km

To Find

( i ) Average Speed

( ii ) Average Velocity

Concept Used

Average Speed

It is defined as total distance travelled per total time

Average Velocity

It is defined as net displacement per total time

Solution

Case - 1 : Average Speed

Total distance , D = A -> B + B -> A

⇒ D = 200 + 200

⇒ D = 400 Km

Total time , t = A -> B + B -> A

⇒ t = 2 + 3

⇒ t = 5 h

Apply formula for Average Speed ,

$\implies \rm A_{Speed}=\dfrac{D}{t}\\\\\implies \rm A_{SPeed}=\dfrac{400}{5}\\\\\implies \rm A_{Speed}=80\ Km/h$

Case - 2 : Average Velocity

Net displacement , d = A -> B - B -> A

⇒ d = 200 - 200

⇒ d = 0 Km/h

Total time , t = 5 h [ ∵ Already found ]

Apply formula for Average Velocity ,

$\implies \rm A_{Velocity}=\dfrac{d}{t}\\\\\implies \rm A_{Velocity}=\dfrac{0}{5}\\\\\implies \rm A_{Velocity}=0\ Km/h$

More Info

• Speed : It is defined as distance travelled per unit time
• Velocity : It is defined as displacement per unit time
• Distance : It is defined as how much ground occupied by an object
• Displacement : It is defined as how far out of place an object is
• SI unit of Speed / Velocity is m/s
• SI unit Distance / Displacement is meter
• SI unit of time is second