An electric toy car with a mass of #4 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 #7/2 m/s#? Physics Electrical Energy and Current Electric Power 1 Answer Narad T. Aug 14, 2017 The time is #=1.17s# Explanation: The power is #P=UI# 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=4kg# The speed is #v=7/2ms^-1# so, #E=1/2*4*(7/2)^2=49/2J# Let the time #=ts# #E=Pt# #t=E/P=(49/2)/21=1.17s# Answer link Related questions What is the SI for a unit of power? What is a kilowatt-hour? Where can I see an electric circuit in my home and car? Why do batteries run down? When an electrochemical cell no longer works, can it be recharged before it can be used again? How does a rechargeable battery work? Question #129ab Why is electric power transmitted at high voltages? What is a unit of electrical current? What is an electric current that reverses its direction in a regular pattern? See all questions in Electric Power Impact of this question 1075 views around the world You can reuse this answer Creative Commons License