Preliminary Information: To explore the definition of work and learn how to find
ID: 2288767 • Letter: P
Question
Preliminary Information: To explore the definition of work and learn how to find the work done by a force on an object.
The word "work" has many meanings when used in everyday life. However, in physics work has a very specific definition. This definition is important to learn and understand. Work and energy are two of the most fundamental and important concepts you will learn in your study of physics. Energy cannot be created or destroyed; it can only be transformed from one form to another. How this energy is transferred affects our daily lives from microscopic processes, such as protein synthesis, to macroscopic processes, such as the expansion of the universe!
The net work done on an object is the sum of the work done by each individual force acting on that object. In other words,
The net work can also be expressed as the work done by the net force acting on an object, which can be represented by the following equation:
Now to the Questions:
Knowing the sign of the work done on an object is a crucial element to understanding work. Positive work indicates that an object has been acted on by a force that tranfers energy to the object, thereby increasing the object's energy. Negative work indicates that an object has been acted on by a force that has reduced the energy of the object.
Intro Figure 1
Part F
1. Which of the following statements accurately describes the sign of the work done on the box by the force of the push?
A. Positive
B. Negative
C. Zero
2. Which of the following statements accurately decribes the sign of the work done on the box by the normal force?
A. Positive
B. Negative
C. Zero
3. Which of the following statements accurately decribes the sign of the work done on the box by the force of kinetic friction?
A. Positive
B. Negative
C. Zero
4. Which of the following statements accurately decribes the sign of the work done on the box by the force of gravity (i.e., the weight)?
A. Positive
B. Negative
C. Zero
Explanation / Answer
1. A Positive
2. since angle = 90, W = 0
c. zero
3. B. negative
4. C. zero
5. this will depend on coefficient of friction
so 0<W<1.75E4 so third options
6. angle = 90 - theta
so W = w d cos(90- theta)
so second choice
7. so gravity is conservative and you come back to the same point W = 0
8) W = 1/2 k x^2
so none of the choices