Question

Please help ASAP. A car engine with a mass of 1750 kg can exert 215 000 W. a) How long will it take the car to reach 95.0 km/h if the car is 100% efficient? b) If it actually takes the car 6.5 s to reach 95.0 km/h, what is the efficiency of the car?

Answer 1

QUESTION①)

✔ First step : calculate the kinetic energy that this car requires to reach 95 km/h

95/ 3,6 ≈ 26,4 m/s

Ec = ½ m x V²

With Ec in J; m in kg; and V in m/s

• Ec = ½ 1750 x 26,4²
• Ec ≈ 610 000 J

✔ Knowing that the car has a p power of 215,000 W, so :

T = E/P

• T = 610 000/215 000
• T ≈ 2.8 s

The car takes 2.8 s to reach 95 km/h

QUESTION②)

N = 2,8/6,5 x 100 = 43.07

The car efficiency is 43 %