An electric toy car with a mass of #15 kg# is powered by a motor with a voltage of #8 V# and a current supply of #3 A#. How long will it take for the toy car to accelerate from rest to #4 m/s#?

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Answer 1 · 2017-03-05T15:58:45

#t=5s#

Electrical power is given by

#P=IV#

and mechanical power by

#P = E/t#

so

#E/t = IV#

We can calculate the kinetic energy, #E#, by

#E = 1/2mv^2 = 1/2 xx 15 xx 4^2 = 120J#

The question is asking about time, so

#t = E/(IV) = 120/(8xx3) = 5s#