An electric toy car with a mass of #5 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
Nov 13, 2016

Given

#V->"voltage supplied to motor of toy car"=4V#

#I->"current supplied to motor of toy car"=2A#

#v->"velocity gained by the car "=3m/s#

#m->"mass of thecar "=5kg#

Let time taken to gain the velocity be t sec

Now #"Power"(P)=IxxV=2xx4W=8W#

The electrical energy spent in t sec will go to increase the velocity of the car from zero to #3m/s#.

So

#Pxxt=1/2xxmxxv^2#

#=>8xxt=1/2xx5xx3^2#

#=>t=(5xx9)/(2xx8)=2.8125s#