Q. 244.3( 7 Votes )

# Abdul, while driving to school, computes the average speed for his trip to be 20 km h^{-1}. On his return trip along the same route, there is less traffic and the average speed is 30 km h^{-1}. What is the average speed for Abdul’s trip?

Answer :

Let us assume the school to be at distance x km from where Abdul starts

Suppose the time taken while driving to school is *t*_{1}

Average speed = 20 km/h

Time taken,

On returning from the trip the average speed is 30 km/h

Let, the time taken for the return trip is*t*

_{2}

Time taken,

Now, total distance of the whole trip from going to trip to returning back to school is:

Total distance =*x*+

*x*

= 2*x* Km (3)

Total Time taken = Time taken to go to college +Time taken to return back to school

Solving this equation

=(4)

Now, we will calculate the average speed of the whole trip:

Average speed ==

= 24 km/h

Therefore, the average speed for Abdul’s whole trip from going from to school to return back is 24 Km/h.

Rate this question :

Obtain a relation for the distance travelled by an object moving with a uniform acceleration in the interval between 4^{th} and 5^{th} second.

A car accelerates from 6 ms^{–1} to 16 ms^{–1} in 10 sec. Calculate (a) the acceleration and (b) the distance covered by the car in that time.

A bus increases its speed from 36 km/h to 72 km/h in 10 seconds. Its acceleration is :

Lakhmir Singh & Manjit Kaur - PhysicsA bus is moving with a speed 72 km/h can be stopped by brakes after at least 10 m. What will be the minimum stopping distance, if the same bus is moving at a speed of 144 km/h?

All In One - ScienceDerive the formula: ,where the symbols have usual meanings.

Lakhmir Singh & Manjit Kaur - PhysicsThe speed-time graph of an ascending passenger lift is given alongside.

What is the acceleration of the lift :

(i) During the first two seconds?

(ii) between second and tenth second?

(iii) during the last two seconds?

Lakhmir Singh & Manjit Kaur - PhysicsA car is moving on a straight road with uniform acceleration. The speed of the car varies with time as follows :

Draw the speed-time graph by chooding a convenient scale. From this graph :

(i) Calculate the acceleration of the car.

(ii) Calculate the distance travelled by the car in 10 seconds.

Lakhmir Singh & Manjit Kaur - Physics