Midterm review
First, choose a team…
1.
2.
3.
4.
5.
The Newtons
The Joules
The Watts
The Galileans
The Hookes
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PHYS 131 - Review: Ch. 1 to 8
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PHYS 131 Review: Chapters 1 – 8
Chapter 1: Preliminaries
• units
• significant figures, order of magnitude estimates
• dimensional analysis / sanity checks / diagrams
Chapter 2: 1-D Kinematics
• speed vs velocity / distance vs displacement
• average (speed/acceleration) vs instantaneous
• graphical approach to disp., vel., and acceleration.
• special case of motion at constant acceleration (eg. freefall):
PHYS 131 - Review: Ch. 1 to 8
v = v0 + at
vaver = (v + v0)/2
v2 = v02 + 2a (x – x0)
2
x = x0 + v0 t + ½at2
1
An acceleration vector:
3.
4.
161
64
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PHYS 131 - Review: Ch. 1 to 8
lo
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.
2.
Tells you how fast an
object is moving
Has a direction that can be
determined from two
velocity vectors
Points in the direction of
motion
Is parallel or opposite to
the direction of motion
le
1.
3
In 1-D motion, the slope at a point on a position-vs-time
graph of an object is
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PHYS 131 - Review: Ch. 1 to 8
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2.
The object’s speed at that
moment
The object’s average velocity
at that moment
The object’s instantaneous
velocity at that moment
The object’s acceleration at
that moment
The distance travelled by
the object to that point
Th
1.
4
2
Chapter 3: Vectors
• vectors vs scalars
• vector components; unit vectors
Chapter 4: Motion in two dimensions
• Position and velocity vectors
• Derivatives by components
• 2-D motion at constant acceleration
• Projectile motion:
• parabolic shape
• range equation
• Uniform circular motion
v = v0 + at
vaver = (v + v0)/2
v2 = v02 + 2a (x – x0)
x = x0 + v0 t + ½at2
dproj = 2 (vy0vx0)/g
dproj = v2sin(2Θ)/g
a = v2/r
• Tangential, radial accelerations
• Relative velocities (frames of reference)
PHYS 131 - Review: Ch. 1 to 8
5
Which of the following is true?
1.
A component of a vector is
always larger than the
magnitude of the vector.
2. A component of a vector is
never larger than the
magnitude of the vector.
3. A component of a vector is
sometimes larger than, and
sometimes smaller than, the
magnitude of the vector.
191
47
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PHYS 131 - Review: Ch. 1 to 8
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3
You’re driving down the road at constant speed behind a truck with
a cargo of tomatoes. A tomato falls off the back of the truck.
Ignoring air resistance…
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PHYS 131 - Review: Ch. 1 to 8
..
.
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5.
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4.
95
th
2.
3.
…the tomato falls on the road
about halfway between you and
the truck.
…the tomato hits your car.
…the tomato landing spot will
depend on the height of the
truck.
…the tomato will land at the
back of the truck.
…it’s impossible to tell where
the tomato lands.
…
1.
7
Two projectiles are launched from the same point at the same angle above
the horizontal. Projectile 1 reaches a maximum height twice that of
projectile 2. What is the ratio of the initial speed of projectile 1 to
projectile 2?
One-half
1/√2
The same
√2
Two
Four
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PHYS 131 - Review: Ch. 1 to 8
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1.
2.
3.
4.
5.
6.
8
4
Chapter 5: The laws of motion
• Forces, types of forces
• Newton’s first law; inertial frames
• Newton’s second law: F=ma
• Gravitational force and weight
• Newton’s 3rd law: action-reaction pairs
• Free-body diagrams
• Frictional forces: static vs. kinetic
ΣF = ma
|Ffriction| = µ |Fnormal|
µstatic > µkinetic
PHYS 131 - Review: Ch. 1 to 8
9
An object experiences a net force and a resulting acceleration.
Does the object move in the direction of the force?
1. Yes
2. No
3. Not enough information
to tell
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PHYS 131 - Review: Ch.11 to 8
2
3
10
5
What is the magnitude of the frictional force acting on
the block? The block does not move with respect to the
rotating disk, which is in uniform circular motion.
179
1.
2.
3.
4.
Exactly mv2/r
Less than mv2/r
More than mv2/r
Impossible to tell
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6
PHYS 131 - Review: Ch.
1 1 to 8
2
4 11
3
In the Loma Prieta earthquake in California in 1989, horizontal
ground accelerations of up to 4.0 m/s2 were observed. What’s the
coefficient of static friction that would have been required for an
object to NOT slide in those conditions.
Will always slide
0.25
0.41
4.0
172
4.
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1.
2.
3.
4.
PHYS 131 - Review: Ch. 1 to 8
12
6
A student escaping from her dorm after hours slides down a rope.
As she slides faster and faster she tightens her grip, increasing
the force exerted on her by the rope. When this force is equal in
magnitude to her weight, what happens?
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PHYS 131 - Review: Ch. 1 to 8
12
1
h.
..
4.
5.
She falls
She stops moving
She continues to move
at constant speed
She moves upward
She gets caught
ug
1.
2.
3.
13
Chapter 6: Circular Motion, Other applications
• Dynamics of uniform circular motion:
centripetal acceleration towards center
• curves & banked curves
• non-uniform circular motion
• non-inertial frames and fictitious forces
• resistive forces:
• drag ~ v (typically liquids)
• drag ~ v2 (low density fluids, air)
PHYS 131 - Review: Ch. 1 to 8
a = v2/r
R = -b v
R = - ½ D ρA v2
14
7
If a car turns a corner too quickly, you seem to be
thrown against the door because of
1.
2.
3.
4.
Inertia
The centripetal force
The centrifugal force
The normal force exerted
by the seat
130
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PHYS 131 - Review: Ch. 1 to 8
15
You’re on a ferris wheel moving at constant speed. Where is the
normal force on you by the seat the greatest?
At the bottom
Halfway up the ferris wheel
At the top
It’s the same everywhere
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PHYS 131 - Review: Ch. 1 to 8
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Chapter 7: Energy
• Importance of the system
• Work = force through distance
• “Work is being done by ____ on ____”
•
•
•
•
•
•
•
•
•
W = F||d
Scalar product
Work done by varying forces (graphical, integrals)
Work done by spring
KE = Ekin = ½ mv2
Kinetic energy
Wnet = ∆KE
Work-energy theorem
PEgrav = mg h
Gravitational, elastic potential energies
PEspring = ½ kx2
Internal energies
Conservative vs. non-conservative forces
F = - dU/dx
Forces vs. potential energy
PHYS 131 - Review: Ch. 1 to 8
17
A projectile is launched upwards at an angle θ from the horizontal.
What fraction of its initial kinetic energy does it have at the top of
the trajectory?
1.
2.
3.
4.
5.
6.
sin θ
cos θ
sin2θ
cos2θ
tan θ
tan2θ
75
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29
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7
PHYS 131 - Review: Ch. 1 to 8
18
9
The speed of a particle doubles, and then doubles again because an
external force is doing work on it. Does the external force do more
work during the first doubling or during the second doubling?
1.
2.
3.
4.
The first
The second
The same
Not enough
information to tell
143
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PHYS 131 - Review: Ch. 1 to 8
N
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7
19
Chapter 8: Conservation of Energy
• Isolated vs. non-isolated systems
• Energy transfer mechanisms
• work
• mechanical waves
• heat flow
• matter transfer
• electrical transmission
• EM radiation
• Conservation of mechanical energy in
isolated system
• Power
PHYS 131 - Review: Ch. 1 to 8
∆K+ ∆U + ∆Eint
= W + Tmw + Q +
Tchickens + TET + TEM
P = dW/dt
20
10
If the potential energy of an object is zero,
is the force on the object zero?
1.
2.
3.
Yes
No
Not enough
information to tell
96
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PHYS 131 - Review: Ch. 1 to 8
21
My score on 14 questions was:
<5
5-6
7-8
9-10
11-12
13-14
73
57
22
17
14
14
13
-
12
11
-
10
8
7-
PHYS 131 - Review: Ch. 1 to 8
9-
6
5-
5
<5
1.
2.
3.
4.
5.
6.
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11
Participant Scores
1100
Participant 15203A
1100
1100
1100
Participant 27E496
Participant 1582BE
Participant 27D3C5
1100
Participant 27D3EF
PHYS 131 - Review: Ch. 1 to 8
23
Team Scores
854.29
834.16
811.35
780.76
759.4
The Hookes
The Joules
The Galileans
The Watts
The Newtons
PHYS 131 - Review: Ch. 1 to 8
24
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