An electric toy car with a mass of #8 kg# is powered by a motor with a voltage of #9 V# and a current supply of #4 A#. How long will it take for the toy car to accelerate from rest to #8/3 m/s#?

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Answer 1 · 2017-03-05T15:20:53

#0.79s#

The kinetic energy into the car is given by

#E = 1/2mv^2 = 1/2 xx 8 xx (8/3)^2 = 28.4J#

The power from an electric circuit is given by

#P = IV#

Mechanical power, meanwhile, is

#P = E/t#

so

#IV = E/t#

The question is asking for #t#, so

#t = E/(IV)#

and, plugging in values that we know,

#t = 28.4/(9xx4) = 0.79s#