Phy 2053 Announcements
Exam 1
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Feb 17 Wednesday, 8:20 – 10:10 pm
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Please get there at least 10 minutes early
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Covers Chapters 1 - 5 (includes Lecture on Feb 11 Th)
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Room assignments
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„
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If your last name begins with A through O, you
should go to Carleton 100
If your last name begins with P through Z, you
should go to McCarty C 100
You will be allowed one handwritten formula sheet
(both sides)
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Sample exam from last year posted on website.
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Previous exams & solutions available at Target copy.
Last name, then first name
Test number
Scantron
Test number
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20 questions, multiple choice
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There is only one correct answer to the following question.
(It is not a “freebie”.)
In order to receive credit for this problem, you must correctly code
(“bubble in") your UFID and your 5-digit test number (located at the top
left and right hand corners of this test) onto your scan sheet and also
select the correct response below. Please check now that you have
correctly coded your exam number on the scan sheet.
(1) I have correctly bubbled my UFID number and 5-digit test code.
(2) I won't do this because I don't need really the credit.
(3) I don't know what my UFID number is.
(4) I can't read my test code.
(5) I don't understand what is being asked.
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If your UFID and 5-digit test number is not entered correctly
on your exam, you will not get credit for this question
„
„
Only the scantron will be graded. What you marked on the
exam will NOT count.
However, please circle your answer on the exam as well, in
case the scantron is lost.
(1) I have correctly bubbled my UFID number and 5-digit test code.
(2) I won't do this because I don't need really the credit.
(3) I don't know what my UFID number is.
(4) I can't read my test code.
(5) I don't understand what is being asked.
Exam 1
Phy 2053 Announcements
„
Bring UFID or driver’s license.
„
Bring calculator, pencil and eraser.
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To make the exam fair to everybody, you must stop
writing when the proctors announce that time is up.
We will regard it as cheating if you continue to write.
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Stay in your seat until your exam is collected. If you
finish early, raise your hands; proctors will come to
collect it.
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If you want to avoid the long wait at the end,
either (a) come early and sit at the front or (b)
finish early
Phy 2053 Announcements
„
HW5 due Wednesday Feb 17 at 2 am.
Discussion section quiz as usual for this week.
(on questions in HW5).
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HW6 due next week (Feb 24).
Discussion section quiz next week on HW6.
„
Clicker quizzes for today do not count towards
your final grade.
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Kinematic Equations
Used in situations with uniform
acceleration
v = v o + at
(1)
1 2
∆ x = v o t + at
2
(2)
2
(3)
2
o
v = v + 2 a∆ x
∆x = v average
⎛ vo + vf
t=⎜
⎝ 2
⎞
⎟t
⎠
Important: use the correct sign for x, v and a.
Projectile Motion
The x- and y-directions of motion are
completely independent of each other
„
Projectile
Given Vo and θo
What can you calculate?
Everything!
Max height
Range
Time of impact
X(t) and Y(t) for any time
Vx(t) and Vy(t) for any time
Example 1
Vo = 5 m/s
θ = 30o
h = 80 m
V=?
Other projectile problems
Kinetic and Potential Energy
Kinetic Energy:
potential Energy:
1 2
1 2
KE = mv PE g = mgh PEs = kx
2
2
gravitational
spring
Mechanical energy is conserved if there are no
non-conservative forces (e.g. friction)
(KE + PE g + PE s )i = (KE + PE g + PE s )f
Instantaneous and average velocity
Vinstantaneous = slope of tangent
to x-t curve
v
vaverage =
v
∆x
∆t
Depends only on initial
and final position
Similar concepts:
v
aaverage =
v
∆v
∆t
Example 2
Last years exam:
what is the
average velocity
in the first 30
seconds?
A. 1 m/s
B. 3 m/s
C. 0.3 m/s
D. 0.67 m/s
E. -1.33 m/s
Newton’s Second Law
∑ Fx = max
F
=
ma
∑ y
y
Newton’s Third Law
r
r
F12 = −F21
Free body diagrams
Example 3
Free body diagrams
Pulley is massless and
frictionless. Find the
tension in the string.
A. 50 N
B. 37 N
C. 30 N
D. 20 N
E. 40 N
Example 4
F
θ = 30o
4 kg mass slides down the incline with constant velocity.
Coefficient of kinetic friction = 0.5
(a) Find F.
(b) Find the work done by F on the mass after it has
traveled 0.7 m down the incline.
Work done and power
W ≡ (F cos θ)∆x
Work F ∆x
P =
=
= Fv
∆t
∆t
Wnc = (KEf+PEf) - (KEi+PEi)
ƒs, max = µs n
Friction forces
Example 5
Last year’s exam:
m1 = 5 kg
Coefficient of
static friction
between m1 and
the table is 0.3.
Find max m2 for
the masses to
remain stationary.
Example 6
m2 is changed to 0.6 kg.
m1 remains 5 kg
µs = 0.3.
m1 is initially held at rest and then let
go. What is the friction on m1?
A. 15 N
B. 1.8N
C. 6N
D. 50 N
E. 10 N
Relative Velocity
Adding vectors by components
Bx
v
A
Ay
Ax
v
B
By
v v
A + B = ( Ax + Bx ) xˆ + ( Ay + B y ) yˆ
Example 7
To a cyclist riding north at 2 m/s,
the wind appears to blow towards
the direction 30 degrees south of
west at 1.0 m/s. To a person at
rest, what is the speed and
direction at which the wind is
blowing towards?
Good luck on the exam!