Question

3. A pure eletric car is designed to operate with 12 V battery with a total energy of 2.000107 stored when it is full. When the car moves with constant speed of 20.0 m/s, its electric motor spends 8.00 kw power. a) Find the current used by motor b) Determine the distance you can travel with one charge.

Answer 1

Voltage = V = 12 V

   power = P = 8 kW = 8000 w

P = V * I

a) current = I = P/ V = 8000 / 12 = 666.7 = 667 Amp

b) energy = E = 2 x 10^7 joules

      P = E / t

time = t = E / P = 2 X 10^7 / 8000 = 2.5 X 10^3 sec

speed = v = 20 m/sec = constant

acceleration = a = 0 m/sec^2

distance = S = v * t = 20 * 2.5 X 10^3 = 50 x 10^3 m

                S = 50 x 10^3 m = 50 Km