Download Physics CPA Midterm Review Guide Midterm Topics (percentages

Physics CPA
Midterm Review Guide
Midterm Topics (percentages are approximate)
1. General – Units, Experimental design, Accuracy and precision 6 %
2. Kinematics – knowledge of terms, application of formulas for 1-D motion, graphical
depiction of motion (d vs. t and v vs. t) 19 %
3. Vectors and 2-D motion – vector addition and resolution, projectile motion 15 %
4. Forces and Newton’s Laws – conceptual application of Newton’s Laws and related
terms, application of Newton’s Second law in problem solving 24 %
5. Circular Motion and Universal Gravitation – frequency ,period and linear velocity,
application of Newton’s Second law to uniform circular motion, Law of Universal
gravitation, orbital velocity gravitational field strength. 15 %
6. Impulse and Momentum – Application of the Impulse momentum formula,
relationships among the variables, conservation of linear momentum concepts and
problem-solving 21 %
Note: this review checklist is intended to provide guidance, not a complete list of
things to know.
A. General
Definitions and concepts
1. accuracy2. precision3. Sig figs – how many to use? How do you know?
What determines the number of sig sigs in a measurement?
4. Experimental design
Example:
a) Independent variable
b) Dependent variable
c) Control variables
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B. Kinematics
Definitions and concepts
1. Vector/scalar
2. Distance/displacement
3. Speed/velocity
4. Acceleration
5. Formulas –
6. Free fall: sketch and describe the up and down path of an object in free fall. Identify:
-
Force(s) acting, acceleration at all points, changes in velocity, locations of
max and min velocity
Problems
7. How long does it take a car to cross a 30.0 m wide intersection after the light turns
green, if its acceleration is a constant 2.00 m/s2? (ans. 5.48 s)
After 3.0 s, what is the car’s velocity? (ans. 6.0 m/s)
8.
A motorist drives 100 km from New Jersey to Pennsylvania in 2.50 hours, but
makes the return trip back to Jersey in only 2.00 hours. Calculate the driver’s
average speed and average velocity for the entire trip.
[44.4
km/hr, 0 km/hr]
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9. A racecar accelerates from rest at 7.5 m/s2. How long does it take the car to reach
34 m/s?
[4.5 s]
10.
A motorcycle moving at 25 m/s accelerates uniformly for 8.0 s. What is the
motorcycle’s velocity after it travels 0.260 km?
[4.0 x 101 m/s]
11. Police find skid marks 60 m long showing where a car made an emergency stop. If
the car decelerated at 8.0 m/s2, how fast was the car going?
[31 m/s]
11. A ball is thrown straight up in the air and caught at the same level from which it was
thrown. If the ball was in the air for 3.56 s,
a) what was the initial velocity of the ball?
b) how high did the ball rise?
12. graphical analysis:
a. position-time plots (d vs t)
i)constant speed
ii)+ velocity, + acceleration
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[17.5
m/s]
[15.5 m]
iii) +velocity, -acceleration
iv) – velocity, - acceleration
b. velocity vs. time plots ( v. vs. t)
i)constant speed
iii) +velocity, -acceleration
ii)+ velocity, + acceleration
iv) – velocity, - acceleration
C. Vectors
1. Vector quantities
2. Scalar quantities
3. Vector addition:
A boat’s engine provides a speed of 8 m/s. The boat is directed across the river,
which flows at a right angle to the boat, at a speed of 4 m/s. What is the
resultant velocity of the boat? Give the angle with respect to the river.
8.9 m/s, 27 degrees downriver
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4. Vector resolution
b) A football is kicked at Vi = 20.0 m/s, 37 degrees.
What are the x,y components of the initial velocity of the football?
5. 2-d motion: Sketch:
a) Describe horizontal velocity:
acceleration
b) Describe vertical velocity:
acceleration
a) Problems: A student absent-mindedly slides his phone across the desk when
it slides off the 0.80 m desk with a horizontal velocity of 0.75 m/s.
a) How far away from the base of the desk does the phone land?
b) Calculate the impact speed of the phone with the floor
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D. Forces and Newton’s Laws
Definitions and concepts
1.
2.
3.
4.
5.
6.
7.
ForceEquilibriumNormal forceTension
Friction
gravity
inertia
8. Newton’s Laws
a) Newton’s 1st Law states that:
In order to change velocity, an object must..
b) Newton’s 2nd Law:
c) Newton’s third Law
9. Problems applying Newton’s 2nd Law
a) A force is applied to a 1.0-kg mass/
What magnitude force is required to cause an acceleration of 5.0 m/s2, if the mass is
resting on a frictionless surface?
5N
Suppose instead the mass were on a rough table, with uk = 0.35. What force would
now be required to accelerate the mass to 5.0 m/s2? (ans. 8.4 N)
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b) A force of 400.0 N is used to push a 90.0 kg box across a floor. If the box
accelerates at 2.0 m/s2, what is the coefficient of friction?
[0.25]
c) A 75-kg person stands on a high-speed elevator.
- If the elevator accelerates down at 1.0 m/s2, what is the person’s apparent weight?
660 N
-The elevator car has a mass of 5000-kg. When the elevator accelerates up at 1.0
m/s2, what is the tension in the cable?
5.4 x 104 N
E. Circular Motion
Definitions and concepts
1. centripetal acceleration
2. centripetal force
3. Frequency4. Period
5. examples of types of forces acting as a centripetal force
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a)
b)
c)
d)
tensionfriction
normal
gravitation
6. Newton’s Second law for Uniform circular Motion: Provide formulas to
demonstrate the following:
a) Relationship between centripetal force and mass (ex: which requires more force
to spin on a string at a given frequency: 1 gram or 10 grams?)
b) Relationship between centripetal force and frequency (Ex. As the amusement
park ride spins faster, describe the resulting centripetal force)
c) Relationship between centripetal force and distance? On the playground merrygo-round, which stone will fly off first?
Why does distance matter here, but mass does not?
F. Universal Gravitation
1. Formula:
2. Meaning of inverse square law:
(changes in ‘d’)
If d doubles, Force is
If d is x 1/3, force is
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3. Problems: ‘g’ and gravitation as the centripetal force
Earth mass: 5.98 x 1024 kg
Earth radius: 6.38 x 106 m
a) What is the gravitational field strength for a satellite orbiting at a distance of twice
the earth’s radius?
9.8/4 = 2.5m/s2
b) What is the orbital velocity and orbital period of a satellite that orbits at a distance
3x earth radius from the earth’s surface? v = 3850 m/s, T = 2.89 hours
c) For the satellite in # 2, what is the gravitational field strength at that location? g =
.61 m/s2
d) The orbital velocity of a satellite depends upon the ________________, not the
________________.
As the orbital distance doubles, the velocity __________, and the orbital period
e) For an astronaut of mass 75 kg, calculate the weight on the following earth-like
planets:
-
Planet Alpha
mass 1x earth
radius 2x earth
____________
-
Planet Beta
mass 2x earth
radius 2 x earth
____________
-
Planet Gamma
mass ½ earth
radius ½ earth
____________
-
Planet Delta
mass ½ earth
radius 3/2 earth
____________
-
Planet Epsilon
mass 3 x earth
radius 3/2 earth
____________
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A. Definitions and Formulas
1. Momentum2. Impulse –
3. Under what condition can you apply conservation of momentum:
B. Application of the Impulse formula
1. To maximize change in momentum:
Examples:
2. To maximize force:
Examples:
3. To minimize force:
Examples:
4. A) What is change in momentum upon impact for 2 kg rock that is dropped
from 2 m and hits the ground.
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b) calculate force if impact time is 0.05 s.
5. If a ball of mass 0.05 kg approaches a wall at 10 m/s and bounces straight
back at ¾ vi, what is the change in momentum?
G. Conservation of momentum – definition and general formula:
1. totally inelastic-
2. Elastic-
3. A truck moving at 12 m/s overtakes and collides with a car 1/3 its mass that was
moving at 8 m/s. The vehicles stick together. What is the final velocity of the
combined mass? (11 m/s)
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4. Recoil: sketch and write the formula for two combined masses that start out
together and then “explode” apart:
5. A 50 kg ice skater at rest throws a 20 kg mass away from her with a speed of 2.0
m/s. What is her recoil speed? ( 0.8 m/s)
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