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The power of engine of a car of mass 1200 kg is25 kW. The minimum time required to reach a velocityof 90 km/h by the car after starting from rest is(1) 15 s(3) 60 s1.(2) 25 s(4) 12 s |
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Answer» Velocity = 90 km/hr = 25 m/s. Power = 25 kW = 25,000 W. Work = Kinetic energy ∴ W =1/2 mv² ⇒ W = 375000 Since, Power = Work/time. ⇒ Time = Work/Power ⇒ Time = 375000/25000 ∴ t = 15 s. |
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