An electric toy car with a mass of #5 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 · 2017-11-26T13:51:55

The time is #=0.85s#

The power is

#P=UI#

The voltage is #U=8V#

The current is #I=18A#

The power is

#P=UI=8*18=144W#

The kinetic energy of the car is

#E=1/2mv^2#

The mass is #m=5kg#

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

so,

#E=1/2*5*(7)^2=122.5J#

Let the time #=(t)s#

#E=Pt#

#t=E/P=(122.5)/144=0.85s#