Question

A vehicle with a mass of 1 500 kg is accelerated with a constant acceleration from rest to a speed of 90 km/h up an incline of 1 in 20. The duration of acceleration is 25 seconds. The constant tractive resistance is 220 N. Calculate:

2.1. The engine power required if the efficiency is 80% at the instant when the vehicle reaches

90 km/h. (8)

2.2. The engine power required to move the vehicle at constant speed of 72 km/h the

efficiency is 82%. (6)

Answer 1

$$0.8P=\frac{(220+1500(9.8)(0.05))(90)}{2(3.6)}\\P=14.9\ k W$$

2)

$$0.82P=\frac{(220+1500(9.8)(0.05))(72)}{(3.6)}\\P=23.3\ k W$$