An electric toy car with a mass of #3 kg# is powered by a motor with a voltage of #9 V# and a current supply of #5 A#. How long will it take for the toy car to accelerate from rest to #5/2 m/s#?

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Answer 1 · 2017-04-27T15:59:36

The time is #=0.21s#

Voltage is #U=9V#

Current is #I=5A#

The poweris

#P=UI=9*5=45W#

Velocity is #v=3/2ms^-1#

Mass is #m=3kg#

The kinetic energy is

#KE=1/2mv^2=1/2*3*(5/2)^2=75/8J#

But,

#E=P*t#

The time is #t=E/P=(75/8)/45=0.21s#