An electric toy car with a mass of #3 kg# is powered by a motor with a voltage of #8 V# and a current supply of #18 A#. How long will it take for the toy car to accelerate from rest to #7 m/s#?

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Answer 1 · 2018-06-19T14:10:30

The time is #=0.51s#

The power is

#P=UI#

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

The voltage is #U=8V#

The current is #I=18A#

The power is

#P=UI=8xx18=144W#

The kinetic energy of the car is

#E=1/2mv^2#

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

The speed is #v=7ms^-1#

So,

The kinetic energy is

#E=1/2mv^2=1/2xx3xx(7)^2=73.5J#

Let the time #=(t)s#

#E=Pt#

#"Energy=Power" xx "time"#

The time is

#t=E/P=(73.5)/144=0.51s#