PHY 2049 Test 1 Flashcards
(154 cards)
1
Q
Length (L) SI unit
A
meter (m)
2
Q
Mass (M) SI unit
A
kilogram (kg)
3
Q
Time (T) SI unit
A
second (s)
4
Q
Electric Current (A) SI unit
A
ampere (A)
5
Q
Absolute Temperature (theta) SI unit
A
kelvin (K)
6
Q
Luminous Intensity (I) SI unit
A
candela (cd)
7
Q
Amount of substance (n) SI unit
A
mole (mol)
8
Q
Tera-
A
10^12
9
Q
Giga-
A
10^9
10
Q
Mega-
A
10^6
11
Q
Kilo-
A
10^3
12
Q
Hecto-
A
10^2
13
Q
Deca-
A
10^1
14
Q
Deci-
A
10^ -1
15
Q
Centi-
A
10^ -2
16
Q
Milli-
A
10^ -3
17
Q
Micro-
A
10^ -6
18
Q
Nano-
A
10^ -9
19
Q
Pico-
A
10-12
20
Q
Reduces long numbers to manageable width
A
Scientific Notation
21
Q
Size of a number is adjusted by changing the
A
Magnitude (x 10^?)
22
Q
Any meaningful equation must have the same dimensions in the
A
Left and Right sides
23
Q
Things being added must have
A
The same dimensions
24
Q
Exponents and trig arguments must be
A
dimensionless
25
The pressure in fluid motion depends on its
Density and Speed
26
P=
M/LT^2
Density (p) = M/L^3
Speed (v) = L/T
P/density = speed^2
27
Area
A = L^2
28
Volume
V=L^3
29
Speed
v=L/T
30
Acceleration
a=L/T^2
31
Force
F=ML/T^2
32
Pressure (F/A)
p = M/LT^2
33
Density (M/V)
p=M/L^3
34
Energy
E=ML^2/T^2
35
Power (E/T)
P=ML^2/T^3
36
Figure that is reliably known
Significant figure
37
All non-zero digits are
significant
38
Zeros are significant when...
1. Between other non-zero digits
2. After the decimal point AND another significant figure
3. Can be clarified by using scientific notation
39
Number of significant figures
Accuracy
40
When multiplying or dividing (significant figures)
Round the result to the same accuracy as the least accurate measurement
Ex. 4.5 X 7.3 = 32.85 = 33 (2 sig figs)
41
When adding or subtracting (significant figures)
Round the result to the smallest number of decimal places of any term in the sum
Ex. 135 + 6.213 = 141.213 = 141 (3 sig figs)
42
A quantity that has both magnitude and direction
Vector
43
Vectors are represented graphically as
Arrows: directed lines with arrowheads at their ends
44
Row or column vectors are represented as
i for x, j for y, k for z
45
Specify which position in a row or column vector that the accompanying number should go
i, j, and k
46
Unit vectors in the x, y, and z directions
i, j, and k
| Said to have a length of 1
47
Unit vectors are to have a length of
1
48
Magnitude of a vector is calculated by:
[v] = (sq. rt. (vx^2 + vy^2 + vz^2))
49
The direction of a 2-dimensional vector can be specified by the angle it makes with
The positive x-axis
Theta = tan^-1 (vy/vx)
Theta = cos^-1(vx/[v])
Theta = sin^-1 (vy/[v]
50
Given magnitude and direction the components of a vector can be recovered by
vx=[v]cos theta
| vy=[v]sin theta
51
Vector A + Vector B =
Vector C
52
Vector Ax + Vector Ay =
Vector A
53
Vector A = - Vector B if
[Vector B] = [Vector A] and their directions are opposite
54
Vector B = s Vector A has manitude
[B] = [s][A] and has the same direction as A if s is positive or - [A] if s is negative
55
Slide 18
Comeback to
56
Displacement
| Slide 19
```
Vector = x i + y j
[v] = (sq. rt (x^2 + y^2))
Theta = (tan^-1 ([v])
vx = v cos theta
vy = v sin theta
```
57
Slide 21
comeback to
58
Defined in terms of a set of coordinates or frame of reference
Position
59
In one dimension this is either the x- or y-axis
Position or Frame of reference
60
Measures the change in position
Displacement
| A vector quantity
61
Represented as delta x (if horizontal) or delta y (if vertical
Displacement
| A vector quantity
62
Displacement units
SI: Meters (m)
CGS: Centimeters (cm)
USCS: Feet (ft)
63
Curvy line over straight line
Straight line = Displacement
| Curvy line = Distance
64
Distance may be, but is not necessarily, the
Magnitude of the displacement
65
The rate at which the displacement occurs
Average velocity
66
Velocity (average) =
delta vector x/ delta t
67
Delta t is always
positive
68
Average velocity is a
Vector
| Direction will be the same as the direction of the displacement
69
The limit of the average velocity as the time interval becomes infinitesimally short, or as the time interval approaches zero
Instantaneous velocity
70
Velocity (instantaneous) =
Lim (delta t --> 0) delta vector x/ delta t
71
Indicates what is happening at every point of time
Instantaneous velocity
72
Slope of the tangent to the curve at the time of interest
Instantaneous Velocity
73
The magnitude of the instantaneous velocity
Instantaneous speed
74
Changing velocity (non-uniform) means
An acceleration is present
75
The rate of change of the velocity
Average acceleration
76
Acceleration (average) =
Delta vector v(velocity)/delta t
77
Average accelerations is a
Vector quantity
78
The limit of the average acceleration as the time interval goes to zero
Instantaneous Acceleration
79
Acceleration (instantaneous) =
Lim (delta t --> 0) delta v/delta t
80
When the instantaneous accelerations are always the same, the acceleration will be
uniform
| The instantaneous accelerations will all be equal to the average acceleration
81
The slope of the line connecting the initial and final velocities on a velocity-time graph
Average acceleration
82
The slope of the tangent to the curve of the velocity-time graph
Instantaneous acceleration
83
Slide 29
Comeback to picture
84
Velocity as a function of time
v=v0 + at
85
Displacement as a function of velocity and time
delta x = 1/2 (v0 + v)t
86
Displacement as a function of time
delta x = v0t + 1/2 at^2
87
Velocity as a function of displacement
v^2 = v0^2 + 2a delta x
88
Motion is along the ___ axis
X
89
At t=0 the velocity of the particle is
v0
90
All objects moving under the influence of only gravity are said to be in
Free fall
91
All objects falling near the earth's surface fall with a
Constant acceleration
92
The constant acceleration of objects falling near the earth's surface is called
Acceleration due to gravity and is indicated by g
93
For constant acceleration, two of the equations of motion can be easily derived using
Integration
| dv/dt = a (integrate it)
94
Slide 32, 33
comeback to
95
The position of an object is described by
Its position vector, r
96
The change in an object's position
Displacement
| delta r = r (final) - r (initial)
97
The ration of the displacement to the time interval for the displacement
The average velocity
| v (avg) = delta r/ delta t
98
The limit of the average velocity as delta t approaches zero
The instantaneous velocity
| v= lim (delta t -->0) delta r/delta t
99
An extended object whose parts are at rest relative to each other
Frame of reference
100
To make position measurements we use
Coordinate axis that are attached to reference frames
101
If a particle moves with velocity Vpc relative to reference frame C, which is in turn moving with velocity Vcg relative to reference frame G, the velocity of the particle relative to G is:
VpG = VpC + VCG
| This is called the Galilean transformation equation ****
102
The rate at which velocity changes
Average acceleration
| a (avg) = delta v/delta t
103
The limit of the average acceleration as delta t approaches zero
Instantaneous acceleration
| a = lim (delta t --> 0) delta v/delta t
104
Ways an object might accelerate
1. The magnitude of the velocity can change
2. The direction of the velocity can change (even though magnitude is constant)
3. Both can change
105
No x or x0
v(t) = v0 + at
106
No v(t)
delta x(t) = v0t + 1/2 at^2
107
No t
v^2(t) = v0^2 + 2a(x-x0)
108
No a
Delta x(t) = 1/2 (vo+v(t))t
109
No v0
Delta x(t) = v(t)t - 1/2 at^2
110
Slide 40
Come back to
111
When an object moves in both the x and y direction simultaneously under the influence of a constant gravitational force, the form of two dimensional motion that results is called
Projectile motion
112
Using our assumptions, an object in projectile motion will
Follow a parabolic path
113
The velocity of the projectile at any point of its motion is the
Vector sum of its x and y components at that point
114
Polar and rectangular vector representations are
related
| Slide 43
115
X-direction of Projectile Motion
ax = 0
Vxo=V0 cos theta0 = Vx = constant
x = Vxo t
This is the operative equation in the x-direction since there is uniform velocity in that direction
116
Y-direction of Projectile Motion
Vyo = V0 sine theta0
Take the positive direction as upward
Then: free fall problem only then: ay = -g
Uniformly accelerated motion, so the one dimensional motion equations all hold
117
Slide 46, 47, 48, 49, 50
Come back to
118
A particle moving in a circle with varying speed has
Tangential acceleration
| a of t = dv/dt
119
Tangential acceleration is in addition to
The radial, centripetal acceleration
a of c = v^2/r
a = (sq. rt. (a of c ^2 + a of t^2))
120
Newton's first law
Body at rest remains at rest
| Body in motion stays in motion unless acted upon by an unbalanced EXTERNAL force
121
The property of a body that causes it to remain at rest or maintain constant velocity is called its
Inertia or mass
122
Mass is a
Scalar quantity
123
Units of mass
SI: Kilograms (kg)
CGS: grams (g)
US Customary: slug (slug) or lbm (pound-mass)
124
1 kg =
1000g = 2.2 lbm
125
1 slug =
32.2 lbm
126
Newton's second law
The acceleration produced by forces acting on a body is directly proportional to and in the same direction as the net external for and inversely proportional to the mass of the body.
F= ma
127
The acceleration produced by forces acting on a body is directly proportional to and in the same direction as the net external for and inversely proportional to the mass of the body.
Newton's second law
128
Body at rest stays at rest....
Newton's first law
129
Both F and a in the equation F= m/a are
Vectors
130
All the internal forces in a body, such as the forces between atoms and molecules in it, can be completely ignored because
They do not contribute to acceleration of the object as a whole
131
The magnitude of the gravitational force acting on an object of mass near the earth's surface is called the
Weight (w) of the object
| w = mg
132
Special case of Newton's second law
w = mg
133
g can also be found from the
Law of Universal Gravitation
134
The pound (lb) in the USCS system is ambiguous as whether is measures
Mass or force
135
We define the pound-mass as
0.4536 kg
136
We define the pound-force as
4.45N
137
Pound-mass and pound-force are related through
w = mg
| See slide 55
138
Another lb related unit
The poundal
1 pdl = 1 lbm x ft/s^2
1 lbf = 32.2 pdl
139
F (gravity) =
w = mg
140
Force units
SI: N
USCS: pdl, lbf
141
Mass units
SI: kg
USCS: slug, lbm
142
Types of fundamental forces
1. Strong nuclear force (strongest)
2. Electromagnetic force
3. Weak nuclear force
4. Gravity (weakest)
143
Characteristics of fundamental forces
1. All field forces
| 2. Only gravity and electromagnetic in mechanics
144
Other classes of forces include
Cohesion, adhesion, thrust, drag, friction, lift and shearing force
All of these are based on the electromagnetic interactions between the atoms of various substances
145
According to current understanding there are
4 forces in nature
Two of these operate in the nucleus
All common and familiar forces are either gravitational or electromagnetic in origin
146
Perpendicular to direction of the surface of contact
Normal contact force
147
Forces parallel to surface of contact
Friction
148
The force of springs follows
Hooke's Law
| F = -kx
149
A special diagram showing only the forces acting on a body
Free body diagram
150
Free body diagram
1. Identify all the forces acting on the object of interest
2. Choose an appropriate coordinate system
3. Represent the body as a point and draw the forces in appropriate directions
Slide 60
151
Applying Newton's Laws
1. Make a sketch
2. Draw free body diagram
3. Assign forces to x and y components
4. Apply F = ma and keep track of signs
5. If more than one object, apply Newton's third law
6. Solve
152
If there is more than one object
Apply Newton's 3rd law
153
Whenever one body exerts a force on a second body, the second body exerts a force back on the first that is equal in magnitude and opposite in direction
Newton's 3rd Law
| For every action there is an equal and opposite reaction
154
Newton's third law
For every action, there is an equal and opposite reaction
