Question

during an energy transformation, the total amount of energy stays the same. so, when one type of energy decreases, at least one other type of energy will increase.
read the passage about the next part of the ride. think about how kinetic energy, chemical potential energy, and thermal energy changed.

ellen biked in a straight line along the street. then, to avoid the sun, she moved over to ride under the shade of some trees. but as she pedaled faster and sped up, ellen started to feel hot even in the shade.

decide how each type of energy changed.

	increased	stayed the same	decreased
ellen’s kinetic energy	〇	〇	〇
ellen’s thermal energy	〇	〇	〇

Explanation:

1. Chemical potential energy in muscle cells: Ellen uses energy from her muscle cells (chemical potential energy) to pedal. As she expends energy to pedal faster, this chemical potential energy is converted to other forms, so it decreases.
2. Kinetic energy: Kinetic energy depends on speed (\( KE = \frac{1}{2}mv^2 \)). Since Ellen “sped up,” her speed \( v \) increases, so her kinetic energy increases.
3. Thermal energy: The passage states she “started to feel hot,” indicating her thermal energy (heat) increased (due to energy conversion from chemical/kinetic to thermal, e.g., friction or metabolic processes).

Answer:

• Chemical potential energy stored in Ellen’s muscle cells: Decreased
• Ellen’s kinetic energy: Increased
• Ellen’s thermal energy: Increased

(For the table, mark:

• Chemical potential energy: “Decreased” column.
• Kinetic energy: “Increased” column (already marked in the image, consistent with reasoning).
• Thermal energy: “Increased” column.)