Question

the car Travels at a speed of 80 km per hour for 15 minutes and then at a speed of 40 km per hours for next 15 minutes the average speed of the car is

a. 15.7 m/s
b. 16.7 m/s
C. 17.7 m/s
d. 18.7 m/s

please answer with explaination.​

Answer 1

Answer:

Explanation:

Given :-

1st Case

Speed, v = 80 km/hr

Time, t = 15 min = 0.25 hour

2nd Case

Speed, v = 40 km/h

Time, t = 15 min = 0.25 hour

To Find :-

Average Speed

Formula to be used :-

Speed = Distance / Time

Distance = Speed × Time

Average Speed = Total distance/ Total time

Solution :-

1st Case

⇒ Distance = Speed × Time

⇒ Distance = 80 km/h × 0.25 hour

⇒ Distance = 20 kilometers

2nd Case

⇒ Distance = Speed × Time

⇒ Distance = 40 km/hour × 0.25 hour

⇒  Distance = 10 kilometers

⇒ Average Speed = Total distance/ Total time

⇒ Average speed = (20 km + 10 km)/ (0.25 + 0.25) hours

⇒  Average speed = 30/0.50 km/h

⇒ Average speed = 60 km/h

Converting km/hrs into m/s,

= 60 × 5/18

= 3.33 × 5

= 16.65 m/s

Hence, 16.7 m/s is the average speed of the car.

Answer 2

$\tt{Answer: Opt.b) 16.7 m/s}$

Step by step explanation:

Given: Car travels at a speed of 80km/hour for 15 minutes

We know that,

Distance = Speed × time

Distance travelled in 15 minutes = 0.25 hours

» Distance = 80 km/h × 0.25 hrs = 20 km.

And then at a speed of 40km/hour for the next 15 minutes,

Distance travelled in next 15 minutes = 0.25 hrs

Distance = 40 km/hour × 0.25 hour

Distance = 10 km

Now, Average speed of car = total distance travelled / total time taken

Average speed = (20 km + 10 km)/ (0.25 + 0.25) hours

Average speed = 30/0.50 km/hour

Average speed = 60 km/hrs.

Converting 60 km/hrs into m/s,

Multiplying it by 5/18, we get:

60 × 5/18 = 3.33 × 5 = 16.65

Thus, 16.7 m/s is the avg. speed of the car.

Answer: The average speed of the car is 60 km/hr or 16.7 m/s