Question

A car travels A to B at 60 km/hr and returns to A at 90km/hr. what is the average velocity and average speed?​

Answer 1

Answer:

75km/h

Explanation:

Initial speed from a to b = 60km/h

Distance = 60kms.

Final speed form b to a = 90km/h

Distance = 90kms.

➡Average speed = Total distance / total time taken

➡Average speed = 60 +90 /1 + 1

➡Average speed = 60 + 90 / 2

➡Average speed = 150 / 2

➡Average speed = 75km/h.

AVERAGE VELOCITY

Initial velocity (u) = 60km/h

Final velocity (v) = 90km/h

➡Average velocity = v + u / 2

➡Average velocity = 90 + 60 / 2

➡Average velocity = 150 / 2

➡Average velocity = 75km/h.

Answer 2

Answer:

$\boxed{\mathfrak{ Average \ velocity \ of \ car = 0 \ km/h}}$

$\boxed{ \mathfrak{Average \: speed \ of \ car = 72 \: km/h}}$

Given:

Speed of car from A to B = 60 km/h

Speed of car from B to A = 90 km/h

To find:

(i) Average velocity of car

(ii) Average speed of car

Explanation:

(i) As the car returns to it's initial position i.e. A.

$\therefore$

Displacement of car = 0

$\sf Average \ velocity = \frac{Displacement}{Total \ time} \\ \\ \sf = \frac{0}{t} \\ \\ \sf = 0 \ km/h$

(ii) Let distance between A to B be 'd'

So, Total distance travelled by car = 2d

Let the time taken to travel from A to B be $\sf t_{1}$

As, we know

$\sf speed = \frac{distance}{time}$

Therefore,

$\sf \implies 60 = \frac{d}{t_{1}} \\ \\ \sf \implies t_{1} = \frac{d}{60}$

Let the time taken to travel from B to A be $\sf t_{2}$

Therefore,

$\sf \implies 90 = \frac{d}{ t_{2}} \\ \\ \sf \implies t_{2} = \frac{d}{90}$

Total time for covering 2d distance (t) = $\sf t_{1} + t_{2}$

$\sf Average \: speed = \frac{Total \: distance}{Total \: time} \\ \\ \sf = \frac{2d}{t} \\ \\ \sf = \frac{2d}{t_{1} + t_{2}} \\ \\ \sf = \frac{2d}{ \frac{d}{60} + \frac{d}{90} } \\ \\ \sf = \frac{2d}{ \frac{6d}{360} + \frac{4d}{360} } \\ \\ \sf = \frac{2d}{ \frac{6d + 4d}{300} } \\ \\ \sf = \frac{2d}{ \frac{10d}{360} } \\ \\ \sf = \frac{2 \cancel{d} \times 360}{10 \cancel{d}} \\ \\ \sf = \frac{2 \times 36\cancel{0}}{ \cancel{10}} \\ \\ = \sf 2 \times 36 \\ \\ \sf = 72 \: km/h$