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 #8/3 m/s#?

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Answer 1 · 2018-01-02T13:45:59

The time is #=0.51s#

The power is

#P=UI#

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

The voltage is #U=7V#

The current is #I=3A#

The power is

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

The kinetic energy of the car is

#E=1/2mv^2#

The mass is #m=3kg#

The speed is #v=8/3ms^-1#

so,

#E=1/2*3*(8/3)^2=32/3J#

Let the time #=(t)s#

#E=Pt#

#"Energy=Power" xx "time"#

The time is

#t=E/P=(32/3)/21=0.51s#