An electric toy car with a mass of #4 kg# is powered by a motor with a voltage of #6 V# and a current supply of #7 A#. How long will it take for the toy car to accelerate from rest to #8 m/s#?
1 Answer
Mar 20, 2016
Explanation:
The power input is the product of the voltage and the current.
#P = IV#
#= (6 "V") * (7 "A")#
#= 42 "W"#
The change in kinetic energy for the car is
#Delta "KE" = 1/2 m (v^2 - v_0^2)#
#= 1/2 (4 "kg") ((8 "m/s")^2 - (0 "m/s")^2)#
#= 128 "J"#
Thus, the time needed is the energy divided by the power.
#t = frac{Delta "KE"}{P}#
#= frac{128 "J"}{42 "W"}#
#= 3.05 "s"#
