Physics 9702 · AS & A Level · Energy conservation

Energy conservation — practice question

An electric car moves along a straight horizontal road at a steady speed of $70\,\text{km h}^{-1}$ over a distance of $80\,\text{km}$ and takes energy $E$ from its battery. The overall resistive force on the car is proportional to $(\text{speed})^2$. Assume that the electric motor is $100\%$ efficient. What amount of energy is taken from the battery when the car moves at a steady speed of $60\,\text{km h}^{-1}$ over the $80\,\text{km}$ straight horizontal road?

  • A$0.73E$
  • B$0.86E$
  • C$1.2E$
  • D$1.4E$

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