   INTRODUCTION

It's Sunday night and you are trying to complete your physics homework. You are trying to somehow modify a problem into the form of a previously solved problem.
It doesn't work all the times and you are wondering what is wrong.

If you are unable to solve physics problems like the ones given for homework, it is not likely that you are having a math difficulty; rather it is more likely that you are having a physics difficulty.

Problems in physics will seldom look the same. Instead of solving problems by copying or by reproducing a previously solved problem, you should utilize your conceptual understanding of Newton's laws to work towards solutions to problems.

In this investigation you will gain a deeper understanding of the concept of net force that will help you solve the various problems assigned.

By the end of this PhysicsQuest you will use your understanding of weight, mass and net force (vector sum of all the forces) to find the value of an individual force or the acceleration.
PROCESS AND RESOURCES

You will be given a series of questions and various links to Internet sites that will help you answer the questions.

Part I.  FORCES

A variety of force types were placed into two broad category headings on the basis of whether the force resulted from the contact or non-contact of the two interacting objects.

1. Define and give an example of each contact forces using
your own words. (Frictional Force, Tensional Force,
Normal Force,  Air Resistance Force, Applied Force and
Spring Force).
PhysicsQuest

PART II. FORCES AND
NEWTON'S SECOND LAW             PART II. FREE-BODY-DIAGRAMS

Free-body diagrams (FBD) are vector diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation.

2. Construct free-body diagrams for the following
situations described at the end of the page: Practice questions: 1, 2, 5, 7, 10 and 11
- Use a ruler and label all the forces.
- Do not show 'boxes' to illustrate an object! Use the
point particle method learned in class!
- Draw the diagrams FIRST and then check your
Part III. NEWTON'S SECOND LAW
Finding Acceleration

The process of determining the acceleration of an object demands that the mass and the net force are known.

3. Which equation should be used to solve for acceleration?

4. Solve the three practice problems given at the bottom
of the section. Include the following in each problem:
- Data
- A labeled FBD of each situation as we do in class.
- The equation(s) for the SNet Force (sum of forces)
- Calculation of acceleration.
- Use g = 9.8 m/s^2
- Check your answers to the problems.      Part IV. NEWTON'S SECOND LAW
Find individual forces.

The objective of this section is to determine the magnitudes of all the individual forces acting on an object if the mass and acceleration of the object are known.

5. Write the three major equations used in this section:
a. The equation for net force,
b. The equation for gravitational force and
c.  The equation for frictional force.

6. Solve practice problems 2, 3, 4 and 5 given at the bottom of
the section.
Include the following in each problem:
- Data
- A labeled FBD of each situation as we do in class.
- The equation(s) for the Net Force (sum of forces)
- Use g = 9.8 m/s^2
- Calculation of individual forces.
- Check your answers to the problems.  WINNER ACTIVITY:
"IDEAS FOR EDUCATORS"
SPRING 2004       Part V. FREE-FALL AND AIR RESISTANCE

The objective of this section is to understand how air resistance works.
Read this section and using your own words answer these questions:

7. What are the two factors (among others) that affect air
resistance?
8. Why do objects which encounter air resistance
ultimately reach a terminal velocity?
9. Why do more massive objects fall faster than less
massive objects? An article on a veterinary journal claimed that "the number of broken bones and other injuries increased with the number of stories the cat had fallen - up to seven stories. Above seven stories, however, the number of injuries per cat sharply declined. In other words, the farther the cat fell, the better its chances of escaping serious injury."

10. Using what you learned about air resistance explain how come cats are
such physics wizards!