An electric toy car with a mass of #3 kg# is powered by a motor with a voltage of #3 V# and a current supply of #7 A#. How long will it take for the toy car to accelerate from rest to #4 m/s#?

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Answer 1 · 2018-04-13T16:27:17

The time is #=1.14s#

The power is

#P=UI#

#"Power"="Voltage"xx"Current"#

The voltage is #U=3V#

The current is #I=7A#

The power is

#P=UI=3*7=21W#

The kinetic energy of the car is

#E=1/2mv^2#

The mass of the car is #m=3kg#

The speed is #v=4ms^-1#

So,

The kinetic energy is

#E=1/2mv^2=1/2*3*(4)^2=24J#

Let the time #=(t)s#

#E=Pt#

#"Energy=Power" xx "time"#

The time is

#t=E/P=(24)/21=1.14s#