Question

Car travels at 54 km per hour for first 20 seconds 36 km for next 30 seconds and finally 18 km for next 10 seconds find its average speed

Answer 1

Answer :

Given -

• Car travels travels at the speed of 54 km per hour for 20 seconds.
• Then, it travels 36 kilometre per hour for next 30 seconds.
• At last, it travels at the speed of 18 km per hour for 10 seconds.

To Find -

• Average Speed ?

Solution -

Speed = Distance/Time

Hence, Distance = Speed * Time

First case :

• Time = 20 seconds
• Speed = 54 * 5/18 = 15 m/s

Distance = 15 * 20 = 300 m

Second case :

• Time = 30 seconds
• Speed = 36 * 5/18 = 10 m/s

Distance = 10 * 30 = 300 m

Third case :

• Time = 10 seconds
• Speed = 18 * 5/18 = 5 m/s

Distance = 5 * 10 = 50 m

Now, Average Speed = Total Distance/Total Time

⇒ Avg. Speed = (300 + 300 + 50)/(20 + 30 + 10)

⇒ Avg. Speed = (650)/(60)

⇒ Avg. Speed = 65/6

⇒ Avg. Speed = 1.083 m/s

So, The average speed of the car is 1.083 m/s.

Answer 2

Answer:

the average speed of the car is 1.8km/s

explanation:

total distance of the car is 108 km

total time taken =60 sec

average speed =Total distance upon total time taken

so,average speed of the car =108/60=1.8km/s