Chapter 5 Dynamics I : Motion along a Line

1
Chapter 5 Dynamics I Motion along a Line

• 5.1 Equilibrium
• 5.2 Using Newtons Law
• 5.3 Mass and Weight
• 5.4 Friction
• 5.5Drag
• 5.6 More Example of Newtons Second Law
• Reading 5.15.4 and 5.6

2
Equilibrium

• Static Equilibrium V 0
• Dynamic Equilibrium V constant

3
Stop to think 5.1 P128Stop to think
5.2 P132Stop to think 5.3 P135Stop to think 5.4
P141

• Example 5.2 P 124
• Example 5.4 P 127
• Example 5.7 P 136
• Example 5.9 P 141
• Example 5.10 P 142

4
Ex.1
5
Ex. 2
With constant v
6
Using Newtons Second Law
7
Ex. 3
8
Mass and Weight

• Weight
• g9.8 m/s2
• The magnitude of the weight force is directly
  proportional to the mass, with g as the constant.

9
Apparent weight
Wapp Fsp
10
Apparent weight is the magnitude of the contact
force that supports the object

• When acceleration is upward
• If elevator moves with constant velocity
• What is apparent weight?
• if elevator has acceleration downward
• What is apparent weight?

11
Friction

• Static friction
• Notice the box remains the rest
• An object remains at rest as long as
• The object slips when

Here µs is called Coefficient of static friction
12
Kinetic Friction

• Once the box starts to slide, the static kinetic
  friction force is replaced by a kinetic friction
• Here µk is called the coefficient of kinetic
  friction

13
Example 5.9 (p141)