An electric toy car with a mass of #7 kg# is powered by a motor with a voltage of #3 V# and a current supply of #9 A#. How long will it take for the toy car to accelerate from rest to #14/3 m/s#?

1 Answer
Mar 19, 2016

#0.202 "s"#

Explanation:

The power input is the product of the voltage and the current.

#P = IV#

#= (3 "V") * (9 "A")#

#= 27 "W"#

The change in kinetic energy for the car is

#Delta "KE" = 1/2 m (v^2 - v_0^2)#

#= 1/2 (7 "kg") ((14/3 "m/s")^2 - (0 "m/s")^2)#

#= 76.2 "J"#

Thus, the time needed is the energy divided by the power.

#t = frac{Delta "KE"}{P}#

#= frac{76.2 "J"}{27 "W"}#

#= 0.202 "s"#