Physics 201 MWF10:20 Fall 1993 (Ford)
Final Exam Chapts. 1--23 in SZY College Physics
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(11 pts) 1. Two blocks move on a horizontal frictionless surface. Initially
block A, with mass 2.0 kg, is traveling to the right with a speed
of 13.0 m/s and block B, with mass 4.0 kg, is traveling to the
left with a speed of 6.0 m/s. The two blocks collide and after
the collision block A is moving to the left with a speed of
3.0 m/s.
a) What is the speed of block B after the collision? Is block
B moving to the left or to the right after the collision?
Ans. v = _______________
direction _________________
b) What is the total kinetic energy of the system of two blocks before and after
the collision?
Ans. before ____________
after ________________
(9 pts) 2. A cylinder with a moveable piston contains 2.0 moles of an ideal gas
at an initial temperature of 250 K. The gas undergoes an adiabatic compression
(Q =0) and the temperature rises to 700 K. For this gas
Cp = 20.8 J/mol·K and
CV = 12.5 J/mol·K. The gas constant is
R = 8.314 J/mol·K. Calculate the work W done by the
gas in this process. Be sure to indicate whether the work done by the gas is
positive or negative.
Ans. __________________
(6 pts) 3. A string is stretched between two fixed supports so that the
tension in the string is 60 N. The string is vibrating in its fundamental
standing wave. The wave speed is 20 m/s and the wavelength is
0.5 m.
a) What is the frequency of the fundamental?
Ans. _______________
b) What is the length of the string?
Ans. _____________
c) What is the mass of the string?
Ans. _____________
(14 pts) 4. The system sketched below is released from rest, and the hanging
block of mass m is observed to move downward a distance of 10.0 m in a
time of 2.0 s. The coefficient of friction between the horizontal surface
and the 8.0 kg block is µk = 0.2. The pulley is massless and
fricitionless. Calculate:
a) the acceleration of the hanging block.
Ans. __________________
b) the friction force acting on the 8.0 kg block while it is moving.
Ans. _______________
c) the tension in the rope connecting the blocks while the blocks are
moving.
Ans. _______________
d) the mass m of the hanging block.
Ans. ________________
(12 pts) 5. A stone is thrown off the roof of a tall building with an initial
speed of v0 = 20 m/s and at an angle of 37° above the
horizontal. It strikes the ground a horizontal distance of 72 m from the base of
the building.
a) What is the height of the building?
Ans. __________________
b) What are the magnitude and direction (angle measured from the horizontal)
of the velocity of the rock just before it strikes the
ground?
Ans. v = ________________
angle ____________________
(12 pts) 6. A rope is wrapped around a wheel with radius 0.80 m. The wheel is
mounted with frictionless bearings on an axle through its center. A block with
mass 2.0 kg is suspended from the end of the rope. After the system is
released from rest the tension in the rope is observed to be 8.0 N.
a) What is the magnitude of the downward acceleration of the block?
Ans. _____________
b) What is the moment of inertia of the wheel?
Ans. __________________
(12 pts) 7. End A of bar AB rests on a frictionless horizontal
surface while end B is hinged. The bar is uniform, is 4.0 m long, and
weighs 50 N. A horizontal force P =90 N is applied to the bar at
end A.
a) What is the normal force the surface exerts on the bar?
Ans. _________________
b) What are the horizontal and vertical components of the force the hinge
exerts on the bar?
Ans. horizontal ________________
vertical _________________
(12 pts) 8. A large hollow plastic sphere is held below the surface of a
freshwater lake (density of the water is 1000 kg/m3) by a cable
anchored to the bottom of the lake. The sphere has a volume of
0.150 m3,
and the tension in the cable is 600 N.
a) Calculate the buoyant force exerted by the water on the sphere.
Ans. ______________
b) What is the mass, in kg, of the sphere?
Ans. ______________
(12 pts) 9. A 0.20 kg block is placed against a compressed spring. The spring
is released and the block travels along a horizontal surface. The coefficient
of kinetic friction between the block and the surface is
µk = 0.40.
After the block has traveled 4.0 m from where it was released its speed
is 6.0 m/s. How much potential energy was initially stored
in the compressed spring? (The block is not attached to the spring.)
Ans. _______________