Newton

1
Newtons Laws of Motion
2
Forces
Types Range
Gravitational Unlimited
Electromagnetic Unlimited
Weak Nuclear ? 10-12 m
Strong Nuclear ? 10-15 m
3
Newtons First Law (Law of Inertia)
If no external force acts, an object maintains
a constant velocity.
4
Mass Gravitational mass mg
Inertial mass mi
mg mi
5
Newtons Second Law
Units of Force
System Mass Acceleration Force
SI kg m/s2
N kg m/s2 British slug
ft/s2 lb slug ft/s2
6
Force of Gravity and Weight
Weight mg
7
Newtons Third Law
Action/Reaction Forces
8
Normal Force
9
Normal Force
N
mg
10
Normal Force
N
mg
11
A man stands on a scale inside a stationary
elevator.
Forces acting on the man
Reading on scale
12
When Moving Upward With Constant Velocity
Forces acting on the man
Reading on scale
13
When Moving Upward With Constant Acceleration
Forces acting on the man
Reading on scale
14
When Moving Downward With Constant Acceleration
Forces acting on the man
a
Reading on scale
15
Applications of Newtons Laws
Tension in strings
q
m
q 60o
m 20 kg
mg 196 N
16
Applications of Newtons Laws
Another method
q
T1
T2
mg
m
17
Applications of Newtons Laws
F 20 N
vo 0
m 5 kg
Dt 5 s
v ?
F
m
Find velocity of block after Dt
18
Applications of Newtons Laws
F -10 N
vo 20 m/s
m 5 kg
v 0
F
m
x
Find distance block moves
19
Find the acceleration of the two block system
Forces on m1
m1
m2
Forces on m2
20
Find the acceleration of the two block system
Mass 1
Mass 2
21
Acceleration down a frictionless incline
q
q
22
Three mass system - find acceleration
T1
T2
F
m
3m
2m
23
Three mass system - find T2
T2
T1
F
m
3m
2m
24
Three mass system - find T1
T1
T2
F
m
3m
2m
25
Three mass system - find T1
Or
T1
T2
F
m
3m
2m
26
Friction
Force of Static Friction
m
27
Friction
Force of Kinetic Friction
v
m
28
Table 5.2
Coefficients Of Friction
Steel on steel 0.74 0.57 Aluminum on steel
0.61 0.47 Copper on steel 0.53
0.36 Rubber on concrete 1.0 0.8 Wood on
wood 0.25-0.5 0.2 Glass on glass 0.94
0.4 Waxed wood on wet snow 0.14 0.1 Waxed
wood on dry snow ------ 0.04 Metal on metal
(lubricated) 0.15 0.06 Ice on ice 0.1
0.03 Teflon on Teflon 0.04 0.04
29
q
q
Acceleration on a rough incline
30
Pulling a block
Pulling a block with constant speed
m
The normal force
31
Pulling a block with constant speed
y
N
F
N
mk
F
q
f
q
m
f
x
mg
mg
The frictional force
32
Pulling a block with constant speed
y
N
F
N
mk
F
q
f
q
m
f
x
mg
mg
The coefficient of friction
33
Frictionless
Find the final speed and the time to side to the
bottom.
mg sinq
mg cosq
q
34
With friction
f mkN
N mg cosq
Find the final speed and the time to side to the
bottom.
f mkmg cosq
mg sinq
mg cosq
q
35
END