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!
A. Your answer is correct. In the collision between the two billiard balls, the rolling ball transfers some of its kinetic energy to the second ball. This transfer of energy can be considered as work, and since the initial ball stops rolling (loses kinetic energy), the change in energy (ΔE) for the system (first ball) is negative.
B. Your answer is correct. When the book is dropped to the floor, it loses gravitational potential energy, which can be considered as work. Since the book's energy decreases (ΔE is negative), your answer is accurate.
C. Your answer is incorrect. The father pushing his daughter on a swing involves a transfer of energy, but it is primarily through the application of a force over a distance. In this case, it is more appropriate to characterize the exchange as work. Since the daughter on the swing gains kinetic energy while swinging higher, the change in energy (ΔE) for the system (daughter and swing) is positive.