Physics 201 MWF10:20 Fall 2001 (Ford)
Final Exam Chapts. 1--17 in Cutnell and Johnson 5th ed
Conceptual multiple choice questions. Circle the correct answer.
(2 pts) 1. When a car is at rest, its horn emits a frequency of 500 Hz. A person standing in the middle of the street hears the horn with a frequency of 540 Hz. Is the car moving toward or away from the person?
a) toward
b) away
(2 pts) 2. Consider a string tied down at both ends. When the tension in the string is increased the wavelength of the fundamental standing wave is
a) increased
b) decreased
c) not changed
(2 pts) 3. A source of sound waves emits sound uniformly in all directions. At a distance of 10 m from the source of sound the sound intensity is 16 W/m2. What is the sound intensity at a distance of 20 m from the source?
a) 2 W/m2
b) 4 W/m2
c) 8 W/m2
d) 16 W/m2
e) 32 W/m2
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(10 pts) 4. A football is kicked from level ground and leaves the ground at a speed of 30 m/s and at an angle of
37°. It strikes the wall of a tall building that is a horizontal distance of 48 m from where the ball was kicked. Neglect air resistance.
a) What is the distance of the football above the ground when it strikes the building?
Ans. _________________
b) What is the magnitude of the velocity of the football just before it strikes the building?
Ans. ____________________
(10 pts) 5. A 120-kg log is pulled down a ramp by means of a rope that is parallel to the surface of the ramp. The ramp is inclined at an angle of 37° from the horizontal. The coefficient of kinetic friction between the log and the ramp is 0.80. The log accelerates down the ramp at 2.0 m/s2.
a) What is the magnitude of the normal force exerted on the log by the ramp?
Ans. ____________________
b) What is the tension T in the rope?
Ans. _________________
(10 pts) 6. A block with mass 5.0 kg is placed against a compressed spring in which 50 J of potential energy is stored. The spring is released and the block travels along a horizontal surface, leaving the spring behind. The coefficient of kinetic friction between the block and the horizontal surface is 0.4. After the block has traveled a distance of 0.8 m from where it is released,
a) how much work has been done on the block by friction?
Ans. ___________________
b) what is the speed of the block?
Ans. ______________________
(10 pts) 7. A skier of mass 50 kg starts from rest at point A. Point B is at the top of a circular hill that has a radius of r = 40 m. Point A is a vertical distance of 9 m above point B. As the skier travels from point A to point B, friction does -2000 J of work on her. As the skier passes through point B, what is
a) her speed
Ans. ________________
b) the normal force exerted on her by the ground.
Ans._________________
(8 pts) 8. Blocks A and B are sliding on a horizontal frictionless surface as shown in the sketch. Block A has mass
mA = 6 kg and block B has mass mB = 4 kg. Initially, block A is traveling east and block B is traveling north. The blocks collide. After the collision, block A is traveling with speed 6 m/s in the direction 37° north of east and block B is traveling east with speed 2 m/s. What is the speed of each of the blocks before the collision?
Ans. A _________________
B ________________
(10 pts) 9. A uniform bar 12 m long is attached at one end to a wall by a frictionless hinge. The bar is held at an angle of 37° with respect to the wall by a horizontal cable. The tension in the cable is 60 N.
a) What is the weight of the bar?
Ans. _________________
b) What are the horizontal and vertical components of the force the hinge exerts on the bar?
Ans. horizontal _________________
vertical ______________________
(9 pts) 10.
a) Two moles of an ideal monatomic gas undergoes a process in which the temperature increases from 27 °C to 227 °C and 400 J of heat flows into the gas.
How much work is done by the gas in this process?
Ans. __________________
Does the volume of the gas increase or decrease?
Ans. ___________
b) In a constant pressure process the temperature of 2.0 moles of an ideal monatomic gas decreases from
327 °C to 27 °C.
How much work is done by the gas in this process?
Ans. __________________
Does the volume of the gas increase or decrease?
Ans. ____________
c) In an isothermal process, two moles of an ideal gas expands and does 3000 J of work.
What is the heat flow Q for this process?
Ans. _______________
Does heat flow into the gas or out of the gas?
Ans. _______________
(8 pts) 11. A block of mass 2.0 kg is attached to a horizontal spring and oscillates back and forth on a frictionless horizontal surface. The spring has spring constant 80 N/m. During its motion the maximum acceleration of the block is 6 m/s2.
a) What is the amplitude of the motion?
Ans. _______________
b) What is the maximum speed of the block during its motion?
Ans. _________________
(9 pts) 12. A uniform solid disk of radius 0.2 m is free to rotate about an axis through its center. The disk is initially at rest. At time t = 0, a constant tangential force of 240 N is applied to the rim of the disk and the disk has an angular velocity of 6 rad/s after the force has been applied for 5.0 s. What is the moment of inertia of the disk, about an axis through its center?
Ans. ____________________
(5 pts) 13. A student is measuring standing wave frequencies for a string that is tied down at both ends. The speed of transverse waves on the string is 80 m/s and is kept constant. The student finds two successive standing wave frequencies to be 120 Hz and 140 Hz. The 120 Hz standing wave is not the lowest frequency standing wave .
a) What is the fundamental frequency?
Ans. ________________
b) What is the length of the string?
Ans. _________________
(5 pts) 14. Two loudspeakers are vibrating in phase. They are set up as shown in the sketch and point C is located as
shown. The speed of sound in air is 343 m/s. The speakers emit sound waves of the same frequency f. What is the smallest frequency f that will produce destructive interference at point C?
Ans. ________________