Are my answers correct?
Identify each energy exchange as primarily heat or work and determine weather the sign of ?E 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 ?E is negative for the system.
B. A book is dropped to the floor.(The book is the system).
My answer= work and ?E is negative
C. A father pushed his daughter on a swing. (the daughter and the swing are the system)
My answer= work and ?E is positive
Thanks!
Let's analyze each energy exchange to determine whether it is primarily heat or work and whether the sign of ΔE (change in energy) 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.
In this scenario, work is involved as the ball stops rolling, which requires external force to be applied to stop the movement. So, the energy exchange is work. And since the ball stops rolling, the change in energy (ΔE) for the system is negative because the system loses energy due to the collision.
Your answer is correct: Work, and ΔE is negative for the system.
B. A book is dropped to the floor. (The book is the system)
When a book is dropped, it falls due to gravitational force, and work is done against gravity. As the book falls downward, the change in energy (ΔE) for the system is negative because the gravitational potential energy is decreasing. So, the energy exchange is work, and the change in energy (ΔE) is negative.
Your answer is correct: Work, and ΔE is negative for the system.
C. A father pushes his daughter on a swing. (The daughter and the swing are the system)
When the father pushes his daughter on a swing, he applies a force to move her back and forth. This force being applied is work, and it increases the system's energy as the daughter gains kinetic energy on the swing. Thus, the energy exchange is work, and the change in energy (ΔE) for the system is positive.
Your answer is correct: Work, and ΔE is positive for the system.
Well done! Your answers are correct for all the given scenarios.