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

Answer 1

u=0
v=90 km/hr or 90*5/18 = 25 m/s

work done= 1/2 mv^2
................... = 1/2*1200*(25)^2 = 375000J

P=dW/dT
25000=375000/T

T=15 seconds

Answer 2

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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