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

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Answer 1 · 2017-03-05T11:56:06

#0.036s#

Energy applied to the toy car is calculated as kinetic energy,

#E = 1/2mv^2 = 1/2 xx 2 xx (3/2)^2 = 2.25J#

We know that electrical power is

#P = IV#

and mechanical power is

#P = E/t#

so

#IV = E/t#

The question asks about the time taken, so rearrange for time,

#t = E/(IV)#

and, putting in the values that we know,

#t = 2.25/(9 xx 7) = 0.036s#