Consider a student lifting a book upward with a constant velocity. 1. What are f
ID: 1517277 • Letter: C
Question
Consider a student lifting a book upward with a constant velocity.
1. What are forces acting on the book?
2. What is the net work on the book if it moves upwards a distance d?
3. What is the change in kinetic energy of the book?
4. Now consider the system of the earth and the book. What are the internal and external forces on this system?
5. What is the net work being done on the system?
6. What is the change in kinetic energy of the system? As in most problems you will do in Physics 7, you can assume the earth is stationary.
7. Is your answer for the change in kinetic energy for the book depend on whether the earth was part of the system? Explain why it changed or is the same.
Explanation / Answer
1.) two forces are acting on book
force due to student opposite to gravity
force due to gravity towards earth
2.)net work done = ( F -mg) *d
3.)change in Kinetic energy = 0.5mv^2
4.)internal forces are
force applied by student and force due to gravity
external forces
no external forces.
5.)net work done = 0 J
system is not moving
6.)change in KE of system = 0 J
7.)yes, it depend on system in which wether earth exist or not.
in refrence to the observer who is looking at the system when the earth is in system there is no movement os system, while when earth is outside the system then there is a movement of system.