An electric toy car with a mass of #3 kg# is powered by a motor with a voltage of #7 V# and a current supply of #3 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 · 2017-03-04T16:02:13

The time is #=0.45s#

Mass, #m=3kg#

Velocity, #v=5/2=2.5ms^-1#

Voltage, #V=7V#

Current, #I=3A#

Power, #P=IV=7*3=21W#

Energy, #E=1/2mv^2=1/2*3*2.5^2=9.375J#

Energy = Power x time

#E=Pt#

#t=E/P=9.375/21=0.45s#