Chapter 5. Force and Motion - GSU

[Pages:33]Chapter 5. Force and Motion

In this chapter we study causes of motion: Why does the windsurfer blast across the water in the way he does? The combined forces of the wind, water, and gravity accelerate him according to the principles of dynamics. Chapter Goal: To establish a connection between force and motion.

Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Chapter 5. Force and Motion

Topics: ? Force ? A Short Catalog of Forces ? Identifying Forces ? What Do Forces Do? ? Newton's Second Law ? Newton's First Law ? Free-Body Diagrams

Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Force: Properties

1. Push or Pull 2. Acts on an object 3. Force is a vector 4. Force is either a contact force or long range force

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Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Force: Properties

Force is a vector ? The net force is the vector sum of the individual forces

How can we find the individual force?

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Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Major Forces:

1. Weight ? gravitational force

r r pulls the objects down ? determines its direction w = mg magnitude:

m - Mass of the object

m

g = 9.8 s2

- free-fall acceleration

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Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Major Forces:

rr w = mg 1. Weight ? gravitational force

2. Spring Force

Fsp = kx

k - coefficient, which depends

only on geometric parameters of the spring

x =| l | - change in the length of the spring

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Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Major Forces:

1. Weight ? gravitational force

2. Spring Force

Fsp = kx

rr w = mg

r T 3. Tension Force

direction is always in the direction of the rope

magnitude - usually found from the condition of equilibrium

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Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

Major Forces: r r 1. Weight ? gravitational force w = mg

2. Spring Force Fsp = kx

r 3. Tension Force T

4. Normal Force

r n

direction is always perpendicular to the surface

magnitude - usually found from the condition of equilibrium

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Copyright ? 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

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