Physics 201 MWF10:20 Fall 2000 (Ford)
Final Exam Chapts. 1--17 in Cutnell and Johnson 4th ed
Show all your work. Partial credit will be given if earned. Write your
answers in the blanks provided.
(5 pts) 1. Two loud speakers A and B are driven by the same amplifier and therefore emit sound waves in phase and with the same frequency f. Speaker B is 10.0 m to the right of speaker A. Point P is 2.0 m to the right of speaker A and therefore 8.0 m to the left of speaker B. What is the smallest nonzero frequency f for which constructive interference will occur at point P? The speed of sound in air is 343 m/s.
Ans. ______________
(5 pts) 2. You are stopped for a traffic light and an ambulance is on the same road up ahead of you and moving away from you with a speed of 30 m/s. The siren on the ambulance emits sound with a frequency of 600 Hz. The speed of sound in air is 343 m/s. What is the wavelength of the sound waves reaching your ears?
Ans. ______________
(5 pts) 3. Transverse waves on a horizontal string have a frequency of 400 Hz and a wavelength of 0.50 m. The amplitude of the waves is 4.0 mm. How much time is required for a particle of the string to travel through a distance of 10.0 m, as it undergoes its transverse up and down motion?
Ans. ______________
(12 pts) 4. A box weighing 50 N is initially at rest on a horizontal surface. The coefficient of static friction is 0.3 and the coefficient of kinetic friction is 0.2. A force P = 30 N that is at an angle of 53° above the horizontal is applied to the box and the box accelerates along the surface.)
a) What is the magnitude of the normal force on the box?
Ans. _______________
b) What is the magnitude of the acceleration of the box?
Ans. _______________
(11 pts) 5. A rock is thrown from the roof of a 12 m tall building. Just before the rock strikes the ground it has a velocity with magnitude 30 m/s and direction 53° below the horizontal. Ignore air resistance. What are the magnitude and direction of the velocity of the rock just after it is thrown, at the start of its projectile motion?
Ans. v0 ___________________
_______________
(11 pts) 6. A small block with mass 0.40 kg is released from rest at point A that is at the top of a curved track that has the shape of a semicircle of radius 5.0 m. During the motion of the block from point A to point B, the work done by the friction force on the block is -12 J.
a) What is the speed of the block when it reaches point B?
Ans. ________________
b) What is the magnitude of the normal force that the track exerts on the block when the block is moving through point B?
Ans. _______________
(12 pts) 7. On a horizontal surface a block with mass 5 kg is placed against a compressed spring that has 60 J of potential energy stored in it. The spring is released and the block travels off to the right. The coefficient of kinetic friction between the block and the surface is 0.2.
a) What is the speed of the block after it has traveled 2.0 m along the surface? (At this point the blcok is no longer in contact with the spring.)
Ans. _______________
b) How far does the block travel before coming to rest?
Ans. ____________________
(10 pts) 8. A thin rod has a length of 0.20 m and rotates in a circle on a frcitionless tabletop. The axis is perpendicular to the length of the rod at one of its ends. The rod has an angular velocity of 0.50 rad/s and a moment of inertia for this axis of 1.2 × 10-3 kg·m2. A bug (mass = 5.0 × 10 -3 kg) standing at the axis decides to crawl out ot the other end of the rod. When the bug reaches the other end of the rod, what is the angular velocity of the rod?
Ans. _______________
(10 pts) 9. A grindstone in the shape of a disk with a radius of 0.2 m is rotating freely at a constant angular speed of 5.0 rad/s about an axis through its center. You then place a metal bar against the rim of the grindstone and the bar exerts a friction force of 12 N on the grindstone. You find that the grindstone slows to 2.0 rad/s in a time of 8.0 s. What is the moment of inertia of the grindstone about the rotation axis?
Ans. ______________
(11 pts) 10. A uniform ladder 12 m long rests against a vertical frictionless wall. The ladder weighs 450 N and makes an angle of 30° with the wall. There is friction between the ladder and the floor. A man weighing 600 N climbs slowly up the ladder. When he passes the point 11 m along the ladder from the bottom, the ladder starts to slip.
a) When the man is 11 m from the bottom of the ladder, what is the normal force exerted by the floor on the ladder?
Ans. ______________
b) When the man is at this position along the ladder, what is the normal force exerted by the wall on the ladder?
Ans. __________________
c) What is the coefficeint of static friction between the floor and the ladder?
Ans. ______________
(8pts) 11. When 2.0 moles of a monatomic ideal gas expands at a constant pressure of 7.0 × 105 Pa, the volume of the gas increases from 3.0 × 10-3 m3 to 8.0 × 10-3 m3.
a) What is the change in the internal energy of the gas?
Ans. ________________
b) Does the internal energy of the gas increase or decrease?
Ans. ________________
c) What is the heat flow Q for this process?
Ans. _________________
d) Does heat flow into or out of the gas?
Ans. _________________