Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley PowerPoint Lectures for...

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley

PowerPoint Lectures for College Physics, Eighth Edition

Hugh D. Young and Robert M. Geller

Lectures by James L. Pazun

Chapter 5Chapter 5

Applications of Newton’s Laws


Goals for Chapter 5

• To study conditions that establish equilibrium.

• To study applications of Newton’s Laws as they apply when the net force is not zero.

• To consider contact forces and the effects of friction.

• To study elastic forces (such as spring force).

• To consider forces as they subdivide in nature (strong, electromagnetic, weak, and gravitational).


The conditions for a particle to be in equilibrium

• Necessary conditions for an object to settle into equilibrium

– F = 0

– Fx = 0 and Fy = 0


Equilibrium in one dimension – Figure 5.1

Follow worked example 5.1 on page 130


Two dimensional equilibrium – Example 5.2

•Both x and y forces must be considered separately.

•Follow worked example 5.2 on page 130.


An example involving two systems – Example 5.4

•See the worked example on page 132 and 133.

•This example brings nearly every topic we have covered so far in the course.


Let’s examine applications of Newton’s Second Law.

Although this liquid is on a level surface, the liquid is on a slant due to different accelerations.


A two-cart train – application II

•Please refer to the the quantitative solution on the bottom of page 134.


Application III - Example 5.5

•This experiment works in your car, a bus, or even an amusement park ride!

•Please refer to the worked example on page 155.


Application IV – Example 5.6

•This sled ride is worked out for you on pages 135-136.


Application V – Example 5.7•This problem involves two interactive systems in a common lab experiment.

•Please refer to the worked example on pages 135-136.


Contact force and friction – Figure 5.10

•We need to re-examine problems we formerly did as “ideal”.

•We need to be able to find frictional forces given the mass of the object and the nature of the surfaces in contact with each other.


The microscopic view of friction – Figure 5.11

•A surface will always have imperfections, your perception of them depends on the magnification.

•The co-efficient of friction will reveal how much force is involved.


Friction changes as forces change – Figure 5.12

•Forces from static friction increase as force increases while forces from kinetic friction are relatively constant.


No dependence on surface area – Figure 5.13

•The normal force determines friction and the normal force depends only on mass.


How much effort to move the fridge? Figure 5.14

•Dynamics as in the last chapter with a new force.

•See the worked solution on pages 141 and 142.


Forces applied at an angle – Figure 5.15

•The previous example has one new step if the force is applied at an angle.

•Please refer to the worked example on pages 142 and 143.


A toboggan on a steep hill with friction – Example 5.12

•Refer to the worked example on pages 143 and 144.


Forces in fluids – Figure 5.18

•This topic is fully developed in advanced courses.

•Conceptually, observe the drag as objects fall through “thicker” liquids.


Elastic forces – Figure 5.19

•Springs or other elastic material will exert force when stretched or compressed.


Stretch a spring to weigh objects. Figure 5.20

•The force settings on the spring are calibrated with mass standards at normal earth gravity.

•The spring scales are often calibrated in force (N) and mass (kg).


There are a variety of force laws in nature.

• Gravitational interactions

• Electromagnetic interactions

• Strong interaction

• Weak interactions

• A “holy grail” of physics is the unified field theory. The goal will be to find the overriding principles that give rise to each of these very similar phenomena.

Copyright © 2007 Pearson Education, Inc. publishing as Addison-Wesley PowerPoint Lectures for...

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