an object moves from point p to q with an average speed of 60m/s and comes back from point q to p with an average speed of 144km/h . what is the average speed of whole journey in m/s?

The only difficulty here is that they use different unit of speed.

we need 144 km/h to m/s
144 km/h = 144000 m / 3600 seconds
= 400 m/s

let the distance from p to q be x m
time for first leg of trip = x/60 s
time for 2nd leg = x/400 s

avg speed = total distance over total time

so you need to add x/60 + x/400
then divide that into the total distance

I will let you do that, let me know what you got.

To find the average speed of the entire journey in m/s, we need to first calculate the total distance traveled during the entire journey.

Given:
Average speed from point P to Q = 60 m/s
Average speed from point Q to P = 144 km/h

Step 1: Convert the average speed from km/h to m/s.
To convert km/h to m/s, we divide by 3.6 since there are 3.6 meters in a kilometer.
144 km/h ÷ 3.6 = 40 m/s

Step 2: Calculate the time taken from point P to Q and from point Q to P.
To find the time taken, we use the formula: time = distance ÷ speed.

Let's assume the distance from P to Q is d. Therefore:
Time taken from P to Q = d ÷ 60

Similarly, let's assume the distance from Q to P is also d. Therefore:
Time taken from Q to P = d ÷ 40

Step 3: Calculate the total distance traveled during the entire journey.
Since the distance from P to Q and Q to P is the same, let's represent the distance as "d".
Therefore, the total distance traveled during the entire journey is: 2d.

Step 4: Calculate the total time taken for the entire journey.
Since the time taken from P to Q and Q to P is the same, let's represent the time as "t".
Therefore, the total time taken for the entire journey is: 2t.

Step 5: Calculate the average speed of the whole journey.
Average speed = Total distance ÷ Total time

Average speed = (2d) ÷ (2t)
Average speed = d ÷ t

Since the distance traveled and time taken are the same for both legs of the journey, the average speed of the whole journey will be the same as the average speed from P to Q or Q to P.

Therefore, the average speed of the whole journey is 60 m/s.