Question

Example 8.2 The odometer of a car reads 2000 km at the start of a trip and 2400 km at the end of the trip. If the trip took 8 h, calculate the average speed of the car in km h- and m s.​

Answer 1

AnswEr :

As per the provided information in the given question, it has been stated that the odometer of a car reads 2000 km at the start of a trip and 2400 km at the end of the trip and the train took 8 hours to travel the distance.

We've been asked to calculate the average speed of the car in km/h and m/s.

In order to calculate the average speed, we need total distance travelled and total time taken.

$\longrightarrow\tt { Total \; distance = (2400 - 2000) \; km}$

$\longrightarrow\tt { Total \; distance = 400 \; km}$

And, the total time is 8 hours. As it is know to us that, average speed refers to the total distance travelled by the object divided by total time. So,

$\longrightarrow \boxed{\tt{ Speed_{(Avg)} = \dfrac{Total\; distance}{Total \; time} }} \\ \\ \longrightarrow \tt{Speed_{(Avg)} = \dfrac{400 \;km}{8 \; h} }\\ \\\longrightarrow \underline{\boxed{\tt{ Speed_{(Avg)} = 50 \; km \; h^{-1}}}}$

Therefore, average speed in km/h is 50 km/h. Now, in order to calculate average speed in m/s. We need to convert distance into metres ans time into seconds.

• 400 km = 400,000 m
• 8 hours = 28,800 seconds

$\longrightarrow \boxed{\tt{ Speed_{(Avg)} = \dfrac{Total\; distance}{Total \; time} }} \\ \\ \longrightarrow \tt{Speed_{(Avg)} = \dfrac{400000 \; m}{28800 \; s} }\\ \\\longrightarrow \underline{\boxed{\tt{ Speed_{(Avg)} = 13.88 \; m \; s^{-1}}}}$

Therefore, average speed in m/s is 13.88 m/s.

Answer 2

Answer:

50 km/h

Explanation: Starting distance = 2000km

After the trip = 2400km

Total Distance = 2400 - 2000

=400km

time = 8h

SPEED = distance / time

= 400/8

= 50km/h

NOW, in m/s

= 50 * 1000/3600

= 13.88 m/s