An electric toy car with a mass of #5 kg# is powered by a motor with a voltage of #1 V# and a current supply of #6 A#. How long will it take for the toy car to accelerate from rest to #4/5 m/s#?

1 Answer
Jan 11, 2017

It will take only 0.27 s to reach this speed.


This problem will be solved using energy considerations, demonstrating the ease with which energy connects different situations - electrical and mechanical.

Given the current and voltage supplied to the motor, we can calculate the power output:

#P=IxxV = 6# watts

This means that work is being done on the car at a rate of 6 joules per second.

For the rest of the problem, we will continue to work in energy terms.

The kinetic energy of the car, must change from zero to

#K=1/2 mv^2 = 1/2 (5)(4/5)^2= 1.6 J#

Since work is being done at 6 J/s, the time required will be:

#(1.6 J)/(6J/s) = 0.27 s#