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Physics GK · Q30

Law of Motion

Competitive Exams · Physics GK · question 30

Q30

Car travels from A to B at a speed of 40 km/h and returns back at a speed of 60 km/h. Its average speed will be

A.
40 km/h
B.
48 km/h
Answer
C.
50 km/h
D.
60 km/h

Answer: Option B

Solution

Answer: Option B
Solution:
Understanding Average Speed:
Average speed isn't just the simple average of two speeds. It's about the total distance covered divided by the total time taken.

Let's break it down:
Imagine the distance between A and B is 120 km (we can choose any distance, this makes the calculation easy).

Going from A to B:
Speed = 40 km/h
Distance = 120 km
Time = Distance / Speed = 120 km / 40 km/h = 3 hours

Returning from B to A:
Speed = 60 km/h
Distance = 120 km
Time = Distance / Speed = 120 km / 60 km/h = 2 hours

Calculating Average Speed:
Total distance = 120 km + 120 km = 240 km
Total time = 3 hours + 2 hours = 5 hours
Average speed = Total distance / Total time = 240 km / 5 hours = 48 km/h

Therefore, the correct answer is B: 48 km/h
Remember: Average speed depends on both the distance and the time taken for each part of the journey. It's not simply adding the speeds and dividing by two.