Download PHYS 1401 Test 1

PHYS 1401
Instructions:
Sample Test Questions
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Exam credit is based on your individual work and explanations in your own words.
The answer alone may be worth nothing. Reciting work and words from another
source, e.g. your textbook, a website, etc., is never an acceptable answer and will
likely receive little or no credit.
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Final answers and units must be clearly indicated by boxing, circling, or underlining.
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Unnecessary and/or incorrect work subtracts from correct work.
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Writing that is hard to read, e.g. written smaller than the font used on this page,
lightly written, messy, etc, will receive little or no credit.
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The instructor/proctor will not comment on your work during the examination.
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Assume that all numbers are known to 3 significant figures, e.g. 5 meters = 5.00
meters.
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All for-credit work must be written on the exam, no attachments are allowed.
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Point values are written in [brackets] at the beginning of a question.
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One (1) 3”x5” note-card f/b is allowed on each mid-term exam.
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Scientific/graphing calculators are allowed.
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Display or use of a cell phone or wireless device results in a score of zero for the
exam.
g = 9.8 m/s/s
1 mile = 1609m
1 hour = 3600s
1. [1] Convert, showing work, 30 miles per hour into m/s.
2. [1] A graph of the motion of an object moving on an x-axis is shown below? This
motion is best described as (circle best answer)
a) constant positive velocity
b) constant negative velocity
x
c) constant speed
d) constant positive acceleration
t
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3. [2] A car starts at 30m/s and slows uniformly to a stop at a rate of -10 m/s/s. Calculate
the distance required by the car to come to a complete stop.
4. [1] An object is launched at 60 degrees above horizontal with speed 10m/s. Calculate
the horizontal component of the launch velocity.
5. [2] A golf ball is hit such that it leaves the ground with a speed of 15m/s an angle of
70 degrees above horizontal. Assuming level ground and no air drag, how far away does
the ball first hit the ground?
6. [3] A person walks 100m due East, stops, and then walks 200m in a direction 30
degrees North of East. Calculate the magnitude and direction of the sum of the two
displacements of this person.
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7. [2] A 2000kg truck has a forward force of 5000N acting on it and is accelerating
forward at 2m/s/s. Calculate the size the backward force acting on the car.
8. [3] A 100kg object is given a push. After the push, the object continues sliding up a 30
degree inclined plane for some distance before it stops. As it slides upward a frictional
force of 200N acts on the object. Calculate the magnitude of the acceleration of the
object as it slides upward after the push.
10. [1] A ball is tossed directly upwards. Which of the following is true? (circle best
answer)
 The acceleration decreases on the way up, then is zero instantaneously at
the highest point, thereafter becoming a negative constant.
 The acceleration is a positive constant on the way up, zero at the highest
point, and a negative constant on the way down.
 The acceleration is constant at all times while it is in the air.
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11. [1] Given the equation y = At + Bt2 + C, where y is in meters and t is in seconds. What
are the units of the constant B?
___ meters
___ meters/second ___ meters/second/second
12. [1] Mass m1 = 1.9kg and mass m2 = 2.1kg are hung over an ideal pulley with a strong
light string. Calculate the acceleration of mass m2.
Ttop
T1
T2
m1
m2
.
13. [1] Which of the following is true? Circle the best answer and explain for credit.
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The acceleration of an object is always in the same direction as the object is
moving.
The acceleration of an object is always in the same or opposite direction of the
object’s velocity
The acceleration of an object is in the direction of the net force and can point in
any direction whether or not the object is moving.
1. [2] A 1300kg car is driving in a circle of radius 30m on a level parking lot with a speed
of 15m/s. Calculate the net force on the car.
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2. [1] The spin cycle of a front loading washing machine is 1600 revolutions per minute.
Calculate the centripetal acceleration of a piece of clothing that is 25cm from the axis of
rotation.
3. [1] A 100kg person runs up a flight of stairs 8m high in a time of 5 seconds. How much
work was done by gravity on the person for this run?
5. [1] A 55kg child is swinging in her backyard. Her speed at the lowest point of the
swing is 6 m/s. What is her maximum height above the lowest point of the swing?
7. [1] A 1000 kg car moving at +5.0m/s undergoes a complete inelastic collision with a
2000kg car moving at -1.0m/s. Neglecting any external forces, what is the velocity of the
cars after the collision?
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8. [2] A 1000kg car moving at 5m/s collides with a brick wall. After the collision the car is
moving away from the wall at 3m/s. The car was in contact with the wall for a time of
0.020 seconds. Calculate the average force exerted on the car by the wall.
10. [2] A (hollow) hoop with mass 1.1kg and radius 0.08m is released from rest on an
inclined plane from a height above ground level of 50cm. If the hoop rolls without
slipping, how fast is it moving when it reaches ground level?
11. [2] A tangential force of 50 N acts for a time of 10 seconds at the edge of a potter’s
wheel, initially at rest, with radius 0.33m and mass 65kg. Calculate the rotational
velocity at the end of the 10 seconds.
12. [2] A light beam of length L = 4.2m is in rotational equilibrium with a 42kg mass at
one end and a 35kg mass at the other end. Calculate the distance d in the diagram.
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13. A disk with rotational inertia I1  2kg  m2 and radius 25cm is rotating at
i  12rad / s about a vertical frictionless axis as shown below. The disk is dropped onto
a disk with I 2  4kg  m2 with the same radius. Later the two disks are rotating at the
same rotational rate  f . The questions below refer to the two disks as a system.
a) [1] Is the angular momentum of the system conserved? _____
b) [1] Is the kinetic energy of the system conserved? ____ If so, why? If not, why not?
c [2] Calculate  f .
7. The position of an oscillating mass-spring system is given by x = (0.05)cos(60t), where
x is in meters and t is in seconds.
a) [1] Calculate the frequency of the oscillations.
b) [1] Calculate the maximum speed of the mass.
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8. An object weighs 1N in air and 0.40N when suspended submerged in water.
The density of water is 1000kg per cubic meter.
a) [1] How large is the buoyant force on the object? How do you know?
b) [3] Calculate the density of the object in grams per cubic centimeter.
10. [2] The transverse wave speed on a string is 60m/s. The string is fixed at both ends
and is 3m long. Calculate the frequency of fundamental vibrations on this string.
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11. [3] On a stove, 3kg of water are heated with a 1000W element. If the initial
temperature of the water is 20C, calculate the temperature of the water after 5 minutes.
The specific heat of the water is 4186 J/(kgC). Assume no heat loss to the environment.
12. A copper bar with k = 401 watt/(meter-kelvin) has one end held at 0C and the other
end held at 200C. The bar has a cross-sectional area of 8  10 5 m 2 and a length of 1
meter. Calculate the heat current through the rod.
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