An electric toy car with a mass of #4 kg# is powered by a motor with a voltage of #7 V# and a current supply of #9 A#. How long will it take for the toy car to accelerate from rest to #3/2 m/s#?

1 Answer
May 16, 2017

To accelerate the object from rest to 1.5#ms^-1# the battery need to do some work on it we can say the work by
#W=1/2m(v_f^2-v_i^2)#
which is ,
#4.5J #

now the electrical energy is equal to =#i^2Rt# or #Vit#

the electrical energy is equal to the mechanical work done , hence

#4.5=Vit#

so , #(4.5)/(7*9)=t=0.07sec#