Question

which of these situations involves a decrease in chemical potential energy and an increase in kinetic energy?
a) a race car is refueled at a pit stop.
b) a marble accelerates down a ramp.
c) a cell phones battery is being recharged.
d) a battery - powered toy car accelerates from rest.

Explanation:

• Option A: Refueling a race - car at a pit stop is just adding fuel (increasing chemical potential energy in the fuel), there is no conversion from chemical potential energy to kinetic energy in this action.
• Option B: A marble accelerating down a ramp involves a change in gravitational potential energy (not chemical potential energy) to kinetic energy.
• Option C: When a cell - phone's battery is being recharged, electrical energy is being converted into chemical potential energy (stored in the battery), which is the opposite of what we want (a decrease in chemical potential energy).
• Option D: In a battery - powered toy car accelerating from rest, the chemical potential energy in the battery is being converted into kinetic energy of the moving car. As the chemical reactions in the battery occur, the chemical potential energy of the battery decreases, and the kinetic energy of the car (which was at rest initially, so \(K = 0\) initially) increases.

Answer:

D. A battery - powered toy car accelerates from rest.