Need Physics Help!?

Question

I am stuck on this problem and would be really greatful with any help on it. I got part A, but cannot figure out part B.

An electric car is designed to run off a bank of 12.0 V batteries with a total energy storage of 1.90 x 10^7 J.

a) If the electric motor draws 6.00 kW, what is the current delivered to the motor (in A)? I know that this is 500 A.

b) If the electric motor draws 6.00 kW as the car moves at a steady speed of 20.0 m/s, how far will the car travel before it is out of juice (in km)?

Answer 1

Use the power to determine the time the car can run on the energy of the batteries. P = E/t ==> t = E/P, where t is time, E is energy, and P is power. You were given E and you calculated P. Once you know how long it can run, just multiply by the constant speed (also given) to determine how far it will travel.

Answer 2

Power = V*I
so 6,000 =12*I and I = 6,000/12 =500 A
Energy = Force *velocity*time
As force*velocity is power = 6,000 watt
1.9*10^7= 6*10^3*2*10*t
so t=1.9/12*10^3 =158.33s
d=3.17km

Answer 3

for this you need to know that 1 joule is equal to one watt second.


1.9x10^7 / 6000 = number of seconds that it will run

Take that answer and multiply by 20 to get how meters it will go. then divide by 1000 to get km