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Unformatted text preview: PhysZSOUniversity Physics 4/7/03 I pledge on my honor as a student at WKU that
Exam 3 I have neither given nor received aid on this exam.
Name: 1. Indicate if the following statements are TRUE or FALSE by writing the appropriate word in the blank space
that precedes the statement.
The total mechanical energy of a system cannot change.
The gravitational potential energy of a mass can be negative.
The elastic potential energy of a spring can be negative.
Work is the area under the forceversustime curve.
Only the net force acting on an object can do work.
Ifthe velocity of an object remains constant, the work done by the net force is zero.
The work done by the string that conﬁnes a mass to moving in a vertical circle is zero.
Only conservative forces can do work.
The conservation of momentum law states that momentum cannot be created or destroyed.
The work done by a conservative force is independent of the force. 2. Given .2 = 3.00i— 4.00} and E = 5.00i+12.0j . Find the dot product of the two vectors. Find the
angle between the two vectors. 3. Find the position of the center of mass of the object shown below with respect to the lower left comer,
assuming it is cut from a uniform thickness plate. The dimension of a unit is 10 cm. Phys 250 — University Physics Exam 3  Page 2 of 4 April 7, 2003 4. The graph is a plot of the force acting on a 50.0 kg
mass versus the time. a. Find the impulse delivered by the force from t=0 to
t=70 s. b. Find the magnitude of the velocity after the impulse, assuming the mass was initially traveling
at 5.00 m/s. 5. A particle of mass m is released from rest on the downward slope of a loop—the
loop (radius r) at a point such that the force by the track on the particle when it
is at the top of the loop is equal to the weight of the particle. Find the height
above the top of the top of loop where the particle was released. (Draw a force
diagram for the particle when it is at the top of the loop. Indicate the initial and
ﬁnal point. Ans. is not r/2) Phys 250 — University Physics Exam 3  Page 3 of 4 April 7, 2003 6. A 3.00 kg mass is traveling to the right at 4.00 m/s when it has a head on elastic collision with a 12.0 kg mass
that is traveling to the left at 2.00 m/s.
a. What two principles of physics must be satisﬁed in this collision?
b. Write in mathematical form the principles of physics that govern the collision for this particular problem.
0. Solve the resulting mathematical relationships (you must show your solution) to ﬁnd the velocity of each
after the collision. 7. A 1.00 kg block is hanging vertically from a long string. A gun is placed below the block and the 0.010 kg
bullet is shot vertically upward into the block, imbedding itself in the block. The block rises vertically a
distance of 0.450 In. What velocity does the bullet have just before it strikes the block. Phys 250 — University Physics Exam 3  Page 4 of 4 April 7, 2003 8. A 4.00 kg mass is moving along a horizontal frictionless surface at ; \ 2.00 m/s when it suddenly encounters a downward slope of 30°. The /0’H \A/ inclined surface has a force of friction of 15.0 N. After the mass has
traveled 10.0 m along the slope, it encounters a spring of constant 400
N/m. What is the magnitude of the maximum compression of the spring? ...
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This note was uploaded on 12/16/2009 for the course PHYSICS 4A taught by Professor D. v during the Spring '07 term at Evergreen Valley.
 Spring '07
 D. V

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