In: Physics
A 0.836 kg toy car is powered by one 9V battery (9.00 V) connected directly to a small DC motor. The car has an effective energy conversion efficiency of 36.1 % , meaning that 36.1 % of the electric energy applied to the motor is converted into translational kinetic energy. After 7.88 s , the car, which is initially at rest, reaches a speed of 3.43 m / s . What is the average current supplied to the car's motor?
The kinetic energy of the car after 7.88seconds is
Let E be the total electrical energy, the energy converted to the translational kinetic energy is
where is the conversion efficiency.
The total electrical energy that must be supplied by the battery in order to increase translational kinetic energy of the car to K is
Substituting ,
The energy supplied by a system of power P in time t is
The power transferred by the battery of voltage V supplying current is , we have
Solving for current