Dolores Gende: PhysicsQuest: FORCES AND NEWTON'S SECOND LAW

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.

TASK

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).

PART II. FREE-BODY-DIAGRAMS

Free-body diagrams 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 method

learned in class!

- Draw the diagrams FIRST and then check your answers.

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 free-body-diagram of each situation using the

method learned in class.

- The equation(s) for the 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.