Are my answers correct?
Identify each energy exchange as primarily heat or work and determine weather the sign of ΔE is positive or negative for the system.
A. A rolling billiard ball collides with another billiard ball. The first ball (system) stops rolling after the collision.
My answer= Work and ΔE is negative for the system.
B. A book is dropped to the floor.(The book is the system).
My answer= work and ΔE is negative
C. A father pushed his daughter on a swing. (the daughter and the swing are the system)
My answer= work and ΔE is positive
Thanks!
Let's go through each scenario and evaluate whether your answers are correct.
A. A rolling billiard ball collides with another billiard ball. The first ball (system) stops rolling after the collision.
Your answer: Work and ΔE is negative for the system.
Your answer is correct. In this scenario, both heat and work can potentially be involved, but in this case, the primary energy exchange is work. The work done by the first ball on the second ball slows down the first ball, resulting in a decrease in its kinetic energy. Therefore, the change in energy (ΔE) for the system is negative.
B. A book is dropped to the floor. (The book is the system).
Your answer: Work and ΔE is negative.
Your answer is correct. In this scenario, only work is involved. As the book falls to the floor, the potential energy of the book decreases, and this energy is transferred to the surroundings as work. Therefore, the change in energy (ΔE) for the system (book) is negative.
C. A father pushes his daughter on a swing. (The daughter and the swing are the system).
Your answer: Work and ΔE is positive.
Unfortunately, your answer is incorrect. In this scenario, the primary energy exchange is heat, not work. When the father pushes the daughter on the swing, he does work on her, increasing her kinetic energy. However, due to air resistance and other factors, some of this energy is lost as heat to the surroundings. Therefore, the change in energy (ΔE) for the system (daughter and swing) is actually negative.
To summarize:
A. Correct. Work is involved, and ΔE is negative.
B. Correct. Work is involved, and ΔE is negative.
C. Incorrect. Heat is involved, and ΔE is negative.