Question

1. which of the following statements best describes the energy transformation that occurs when a log burns? a. mechanical energy changes to chemical energy. b. chemical energy changes to heat and light energy. c. heat and light energy changes to chemical energy. d. mechanical energy changes to heat and light energy. 17. a ball is rolling up and over a hill. the ball slows down as it moves from position 1 to position 3, and it speeds up as it moves from position 3 to position 5. at which point is the balls kinetic energy being transformed into gravitational potential energy? a. only when the ball rolls from position 1 to position 3. b. only when the ball rolls from position 3 to position 5. c. the entire time the ball is rolling from position 1 to position 5. d. it is not being transformed at any time because kinetic energy cannot be transformed into gravitational potential energy.

Explanation:

For question 16:

• A log has chemical energy stored in it. When it burns, this chemical energy is released as heat and light energy.
• Mechanical energy is not involved in the burning of a log in the way described in options A and D. Option C has the transformation in the wrong direction.

For question 17:

• Kinetic energy is the energy of motion (\(KE=\frac{1}{2}mv^{2}\), where \(m\) is mass and \(v\) is velocity) and gravitational potential energy is \(PE = mgh\) (\(h\) is height).
• As the ball moves from Position 1 to Position 3, it slows down (decrease in \(v\), so decrease in \(KE\)) and its height (\(h\)) increases (increase in \(PE\)). So kinetic energy is being transformed into gravitational potential energy in this segment.
• From Position 3 to Position 5, the ball speeds up (increase in \(v\), increase in \(KE\)) and its height (\(h\)) decreases (decrease in \(PE\)), so gravitational potential energy is being transformed into kinetic energy.

Answer:

1. B. Chemical energy changes to heat and light energy.
2. A. Only when the ball rolls from Position 1 to Position 3.