Question

The power of engine of a car of mass 1200 kg is

25 kW. The minimum time required to reach a velocity

of 90 km/h by the car after starting from rest is

(1) 15 s (2) 25 s

(3) 60 s (4) 12 s
explain brief

Answer 1

Hi there!


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Given :



Initial velocity (u) = 0



Final velocity (v) = 90 km/h = 25m/s.



Mass of car = 1200 kg.



Power of engine = 25 kW = 25000 W



We know that..



Power = work done / time



Work done = 1 / 2 mv²



=> 1/2 × 1200 × 25 × 25



=> 600 × 625



=> 375000 Joule.



Now,



Time = work done / power



Time = 375000 / 25000



Time = 15 secs.



Hence, the required time is 15 secs.




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Thanks for the question!



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Answer 2

Hi there!

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Given :

Mass of the car = 1200 kg.

Power of the engine = 25 kW

Power of the engine = 25000 W

Initial velocity (u) = 0

Final velocity (v) = 90 km/ h

=> 90 × 5 / 18

=> 25 m/s.

Now,

Work done = 1 / 2 × m v²

Work done = 1 / 2 × 1200 × 25 × 25

Work done = 375000 Joule.

We know that,

Power = work done / time.

Time = work done / power.

Time = 375000 / 25000

Time = 15 seconds.

Hence,

The required time = 15 secs.

___________________________

Thanks for the question !

☺️☺️☺️