An electric toy car with a mass of #2 kg# is powered by a motor with a voltage of #4 V# and a current supply of #2 A#. How long will it take for the toy car to accelerate from rest to #3 m/s#?

1 Answer
May 15, 2017

I tried this:

Explanation:

We can say that the power of the motor will be:

#P=VI=4*2=8W#

I would then use the theorem of Work #W# and Kinetic Energy #K# to write:

#W=DeltaK#

#W=1/2mv_f^2-1/2mv_1^2#

dividing both sides by the time we get:

#1/tW=1/t(1/2mv_f^2-1/2mv_1^2)#

#P=1/t(1/2mv_f^2cancel(-1/2mv_1^2))#

because the toy car stars from rest (#v_i=0#).

so we get:

#8=1/t*1/2*2*3^2#

rerranging:

#t=9/8=1.125s#