Physics 201 MWF10:20 Fall 1995 (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.
(9 pts) 1. A large plastic sphere is attached by a vertical rope to
the bottom of a lake. The sphere has mass 60 kg and the tension in the
rope is 510 N. The water in the lake has a density of 1000 kg/m3.
What is the density of the sphere?
Ans. ____________________
(12 pts) 2. A small rock is thrown from the roof of a building. The initial
velocity of the rock has a direction of 37° above the horizontal and
magnitude 30 m/s. The rock strikes the ground a distance of
96 m from the base of the building.
a) What is the height of the building?
Ans. ________________
b) What is the maximum height above the roof reached by the rock
during its motion?
Ans. ____________
c) What is the speed of the rock when it is at its maximum height?
Ans. ____________
(14 pts) 3. Blocks A and B sit on a horizontal surface and are
connected by a horizontal rope. Block B has a mass of
mB = 2 kg.
The coefficient of
kinetic friction between each block and the surface is
µk = 0.4.
A force F = 20 N at an angle of 37° above the horizontal is
applied to block B and the blocks accelerate to the right. While
the blocks are moving, the tension in the horizontal rope connecting them
is T = 4.8 N.
a) While the blocks are moving, what is the magnitude of the friction force
on block B?
Ans. ____________________
b) What is the acceleration of block B?
Ans. ___________________
c) What is the mass mA of block A?
Ans. __________________
(12 pts) 4. A block of mass 5 kg is placed on a vertical compressed spring of
negligible mass. The spring is released and the block travels upward,
leaving the spring behind. The initial potential energy of the compressed
spring was 41 J. When the block is 0.30 m above its initial position,
what is its speed?
Ans. ____________________
(12 pts) 5. A uniform bar that has length 8.0 m is attached by a
frictionless hinge at its lower
end to a vertical wall. The bar is held at an angle of 37° from the
vertical by a horizontal cable. An object with mass 20 kg is suspended
from the end of the bar by a vertical rope. The tension in the horizontal
cable is 340 N.
a) For an axis at the hinge, what is the torque due to the tension in the
horizontal cable?
Ans. __________________
b) For an axis at the hinge, what is the torque due to the tension in the
vertical rope?
Ans. __________________
c) What is the weight of the bar?
Ans. ___________________
(13 pts) 6. A block with mass 0.49 kg is at rest on a horizontal surface.
The coefficient of kinetic friction between the block and the surface is
µk = 0.20. A bullet of mass 0.01 kg and initial horizontal
velocity v0 is fired at the block. The bullet strikes
the block and remains embedded
in it. As a result of the collision the block slides a distance of 0.30 m
before coming to rest.
a) What is the magnitude of the work done by the friction force on the block?
Ans. __________________
b) What was the initial speed v0 of the bullet?
Ans. _________________
(12 pts) 7. A cylinder with a moveable piston contains 3.0 moles of ideal
gas at an initial temperature of 520 °C. The gas has
Cv = 20.8 J/mol·K. Compute the work done by the gas
when its temperature is decreased to 150 °C, if the temperature
decrease is carried out in each of the following ways. (In your answer you
must specify whether the work done by the gas is positive or
negative.)
a) isochoric (
V = 0)
Ans. _______________
b) isobaric (p = 0)
Ans. ________________
c) adiabatic (Q = 0)
Ans. _______________
(8 pts) 8. A standing wave is produced on a string of length 0.45 m that is
stretched with a tension of 120 N. The frequency of the standing wave is
150 Hz. The adjacent nodes of the standing wave are separated by 0.15 m.
a) What is the mass of the string?
Ans. ________________
b) What is the frequency of the next higher frequency standing wave for this
string (the tension is kept fixed)?
Ans. ________________
(8 pts) 9. A source of sound waves emits waves with frequency 300 Hz. The
source is traveling to the right with speed 60 m/s. A man is
to the right of the
source and is moving towards it with a speed of 20 m/s.
The speed of sound in the air is 340 m/s.
a) What is the wavelength of the sound waves at points to the right of the
source, at the location of the man?
Ans. _____________
b) What is the frequency fL of the sound waves detected by
the man?
Ans. _________________