Physics 201 MWF10:20 Fall 2004 (Ford)
Final Exam Chapts. 1--17 in Cutnell and Johnson 6th ed
Show all your work. Partial credit will be given if earned. Write your answers in the blanks provided.
(10 pts) 1. A large disk of radius 0.80 m is rotating about a vertical axis through its center with an angular speed of 6.0 rad/s. The disk has a moment of inertia of 16 kg·m2 for rotation about this axis. A small lead brick that has mass 12 kg is dropped from a very small height onto the disk at its rim. After the lead brick has come to rest relative to the disk, so they rotate together, what is the total kinetic energy of the system?
Ans. ___________________
(12 pts) 2. A brick is pushed up a vertical wall by a force F = 80 N that makes a 53° angle with the vertical, as shown in the sketch. The coefficient of friction between the brick and the wall is 0.40. Starting from rest, the brick travels upward 2.0 m in 0.80 s.
a) What is the acceleration of the brick?
Ans. _____________________
b) What is the normal force that the wall exerts on the brick?
Ans. _____________________
c) What is the mass m of the brick?
Ans. ___________________
(12 pts) 3. A small rock is thrown from the roof of a tall building. The rock has an initial velocity of 20 m/s at 53° above the horizontal. It is observed that the rock strikes the ground a horizontal distance of 60 m from the building. Neglect air resistance.
a) What minimum height about the roof is reached by the rock during its motion?
Ans. _________________
b) What is the speed of the rock when it is at its maximum height?
Ans. ________________
c) What is the height of the building?
Ans. _________________
(10 pts) 4. A uniform beam is 6.0 m long and weighs 120 N. One end of the beam is attached to the wall by a frictionless hinge. The beam is held in a horizontal position by a rope that runs from the other end of the beam to the wall. The rope makes an angle of 37° with the beam.
a) What is the tension in the rope?
Ans. ________________
b) What are the horizontal and vertical components of the force that the hinge exerts on the beam?
Ans. horizontal _______________
vertical ________________
(10 pts) 5. On a horizontal frictionless surface a block of mass 0.50 kg is traveling east at 6.0 m/s and a block of mass 1.0 kg is traveling north at 3.0 m/s. The objects collide and stick together. What is the speed of the combined object after the collision?
Ans. _________________
(4 pts) 6. Two loudspeakers A and B are powered by the same amplifier and emit sound waves in phase and with the same frequency f. At point P in the sketch the interference is destructive. As you walk to the right from P1, the first point you reach where the interference is constructive is P2. P2 is 0.80 m to the right of P1. The speed of sound waves is 340 m/s. What is the frequency f of the sound waves?
Ans. _________________
(10 pts) 7. A small rock with mass 0.20 kg is tied to a string and set in motion in a horizontal circle with constant speed. The string is 6.0 m long and makes a constant angle of 53° with the vertical. What is
a) the tension in the string?
Ans. ___________________
b) the time for the rock to complete one revolution?
Ans. ___________________
(9 pts) 8. A uniform wheel of radius 0.20 m rotates in a horizontal plane about a vertical axis through its center. The moment of inertia of the wheel about the axis is 16 kg·m2. A constant tangential force F = 120 N is applied to the rim of the wheel. Starting from rest, how many revolutions does the wheel turn through in 10.0 s?
Ans. ___________________
(15 pts) 9.
a) 2.0 moles of a monatomic ideal gas undergo a process in which both the pressure and volume change. 2000 J of heat flows out of the gas and the gas expands and does 800 J of work. If the initial temperature of the gas is
800 °C, what is its final temperature?
Ans. ____________________
b) In an adiabatic process for 3.0 moles of an ideal gas, the temperature of the gas increases from 173 K to 323 K. What is the magnitude of the work done? Does the volume of the gas increase or decrease?
Ans. |W| = __________________
volume increases or decreases? __________________
c) 2.0 moles of a monatomic ideal gas expands and does 800 J of work while the pressure is kept constant. If the initial temperature is 800 °C, what is the final temperature?
Ans. __________________
(4 pts) 10. A string of fixed length L is tied to fixed supports at both ends. Three successive standing wave frequencies are 320 Hz, 400 Hz,and 480 Hz. There are other standing wave frequencies both larger and smaller than these three. If the speed of the transverse waves on the string is 200 m/s, what is the length of the spring?
Ans. _________________
(4 pts) 11. Transverse waves on a string have amplitude 5.0 × 10-3 m, wavelength 0.20 m and wave speed 40 m/s. During the wave motion, how long does it take a point on the string to travel from its equilibrium position to a point 5.0 × 10-3 m above its equilibrium position?
Ans. ___________________