Question

Question 4 A car of mass 820 kg has a maximum power of 30 kW and moves against a constant resistance of motion to 910 N. Calculate the maximum speed of the car in the following situation; b)Up an incline (hill) of 8.75° to the horizontal?​

Answer 1

Answer:

P = W / t = m g s / t = m g v       where work by auto = m g s

30 kw = 30000 watts = 30000 J / s

Work wasted = F v       as shown above relating work and power

Work done against incline = m g s sin 8.75  and power against incline

= m g v sin 8.75 = 1222 v Joules / sec

power in moving auto = power available - power lost to friction

power in moving auto = 30000 - resistance = 30000 - 910 v

1222 v = 30000 - 910 v

v = 30000 / 2132 = 14 m/s

Note: constant resistance to motion must mean P = W / t = F s / t = F v