Download Practice Final Exam Questions - Conceptual Physics | PHYS 101N and more Exams Physics in PDF only on Docsity!
Final Exam
Part I: Self-paced Clicker Test Instructions: This part is a self-paced clicker test – you can answer the following 25 problems in any order and take as much time as you wish, as long as you complete the whole test before the 3 hours are up. You can also revisit each problem and change your answer, up to 3 times. Begin by working out the answer for each problem. When you are ready to submit an answer, make sure your clicker is on and joined PHYS101. Do not enter anything at the “TST:” prompt - just use the little buttons with up and down triangles (left side of the clicker) to select which problem you want to answer. Enter the answer (one or more digits/letters or True/False) followed by the green “enter” button. You should get feedback that your answer was received (which doesn’t mean it’s necessarily correct!) Keep your clicker on for the whole duration of the test – that way, you can check what you submitted. (Make sure you have fresh batteries installed) First Cluster of Questions: (Each problem counts 1 point) For the following 9 problems, decide whether the object or person described experiences accelerated motion or not. If the motion is accelerated, enter T(rue), else if a = 0, enter F(alse). Problem 1
A child sits on a merry-go-round turning at constant angular velocity. Accelerated? T /F
Problem 2 A car is driving with constant speed along a freeway that makes a curve, changing the
heading from North to West. Accelerated? T /F
Problem 3
A helicopter is rising, increasing its height by 10 m every second. Accelerated? T /F
Problem 4
A space station is circling Earth on a stable orbit. Accelerated? T /F
Problem 5
An astronaut is floating freely inside the space station in Problem 4. Accelerated? T /F
Problem 6 A car going a steady 60 miles per hour on a straight freeway passes a car going 50 miles
per hour in a different lane. Accelerated? T/ F
Problem 7 A car is braking for a red light, a split second before coming to a complete stop. Acceler-
ated? T /F
Problem 8
An apple falls freely from a tree. Accelerated? T /F
Problem 9 A skyjumper is floating towards the ground suspended on her parachute, long after reach-
ing terminal velocity. Accelerated? T/ F
End of cluster. For the following multiple choice problems, just enter the letter that describes the best answer (only one). Each problem counts 2 points. Problem 10 A heavy box is slowly sliding down a ramp, at constant speed. Which of the following forces is NOT acting on that box: A. Gravity
B. Static Friction
C. Kinetic Friction D. Normal Force Problem 11 For the case described in Problem 10, which statement is true: A. The normal force exactly compensates the force of gravity B. The force due to kinetic friction points in the same direction as the normal force
C. The net sum of all forces is zero
D. There is a net force in the direction of motion
Problem 16 A comet and a planet both circle the sun. The planet is on a circular orbit which takes 3 years to complete. The comet is on a strongly elliptical orbit, where it has the same dis- tance from the sun at the closest point of approach (perihelion) as the constant radius of the planet’s orbit, but the farthest point (aphelion) is 7 times further away from the sun than the planet. Which statement is correct: A. The planet has a larger velocity than the comet at its closest distance from the sun B. Both the planet and the comet have the same velocity when the comet is at its closest distance from the sun C. Both the planet and the comet take the same amount of time for a full orbit once around the sun
D. The comet takes 24 years for one full orbit around the sun
Problem 17 A piece of rubber is attracted towards the metal dome of a large, operating Van-de-Graaf generator. What can you conclude, from this information, about the charge on the dome and the charge on the piece of rubber:
A. Other than that the dome likely has some net charge, we cannot
conclude anything from the information given
B. The charge on the dome must be negative C. The piece of rubber must carry a positive net charge D. Both the piece of rubber and the dome must have a net charge, of opposite sign Problem 18 A light bulb is connected to a battery (forming a simple circuit) and lights up. Two light bulbs of the same kind are connected in series to a second battery, and both of them light up with exactly the same brightness as the first light bulb. What can you conclude? A. The second battery must be identical to the first one B. The second battery delivers double the current to the two light bulbs in series than the first battery delivers to the single light bulb
C. The second battery must have double the voltage (electric poten-
tial difference from + pole to – pole) as the first battery.
D. The second battery delivers only ½ of the current that the first one delivers
Problem 19 You have a permanent iron dipole magnet (a rod of iron magnetized along its axis) and another iron rod that looks identical, but is not a permanent magnet. How can you tell which is which without the aid of any other magnetic material or any way of measuring magnetic fields? A. I hold one rod up to both ends of the other rod. If it is attracted to one end of the other rod but repelled by its other end, than that other rod is the magnet. B. I hold one rod up to the other rod, so that they are aligned end-to-end. Then I ro- tate the first rod, so now its opposite end is next to the second rod’s end. If the first rod is attracted to the second one in one case, but repelled in the other, then the second rod must be the magnet.
C. I find a thin filament and bind it around the middle of one rod. If
the freely hanging rod rotates consistently into the same orienta-
tion during several trials, it is the magnet.
D. I do the same thing as in C, but I observe whether the hanging rod is being pulled towards the same direction during several trials. If so, it is the magnet. Problem 20 For the situation in Problem 19, you also have a spool of wire (many windings) and a powerful battery (that can sustain large currents). Which of the following additional tests could tell you which one of the two rods is the magnet? A. I run a whopping current through the wire and hold one rod after the other close to the spool. Whichever is attracted to the spool must be the magnet.
B. I hold each rod up to the spool (with the whopping current), first
aligned one way and than in the opposite orientation. Only if a
rod is attracted in one orientation and repelled in the opposite
orientation can I be sure that it is the permanent magnet.
C. I check which of the two rods exerts a force on the spool when the current is flow- ing. Only the magnet will do that. D. There is no additional way of telling the two rods apart using the spool of wire and the battery.
Part II: Word Problems Each of these problems describes a process where one kind of energy is converted into another kind, and then possibly that one into a third. Identify all types of energy involved and how they get converted into each other during the process. Answer all questions with several complete sentences, written on a sheet of paper. 2 points for each problem Problem 26 A coke can starts (from rest) rolling down a sloped ramp, with increasing speed and without slipping (neglect rolling friction and air resistance). Identify two different contri- butions to the total kinetic energy of the can and one kind of potential energy involved in this process, and how they are converted into each other. Initially the coke can has no kinetic energy, but some gravitational potential energy rela- tive to the bottom of the ramp. As it rolls down, its potential energy decreases and its ki- netic energy increases by exactly the same amount, keeping the total energy the same. The kinetic energy has two parts: One (1/2 mv^2 ) has to do with the linear motion of the coke can (going downwards along the ramp), while the other is due to the rotation of the can (1/2 I ω^2 ). Problem 27 A cart is rolling along a straight, level track (negligible friction). On its front, it has a large spring mounted horizontally. The cart bumps into an identical cart initially at rest, the spring compresses and then expands and the two carts separate. Assume the collision is completely elastic. Identify at least two different types of mechanical energy involved and describe how they vary before, during and after the collision. How do the carts move after the collision? Initially, the rolling cart has finite kinetic energy (1/2 mv^2 ) while the other cart has zero kinetic energy. Since the track is level, we can ignore gravitational potential energy which is constant throughout. As the cars bump into each other, the spring gets com- pressed and therefore stores some amount of elastic potential energy (1/2 kx^2 ) as the first cart slows down (loses kinetic energy). The push of the spring accelerates the second cart which will increase its kinetic energy, and eventually the spring stretches back into its relaxed state, so that all of the energy is now contained in the kinetic energy of the sec- ond cart. At this point, the first cart has come to a complete stop and the second cart is moving with the same speed that the first cart had initially.
Problem 28 An electron starts out from the negative pole of a battery and travels through the thin wire inside a light bulb. It keeps bumping into the atoms making up the wire, thereby heating them up (ever so slightly), while moving with constant speed. At the end, it returns to the positive pole of the battery. Identify at least 3 types of energy involved and describe which of them change and how. The battery provides an electric field throughout the light bulb wire which exerts a force on the electron and therefore does work. Initially, the electron will increase its kinetic energy (a tiny bit in reality) but then it starts bumping into the atoms of the wire. While the electron is moving from the negative to the positive pole of the battery, it loses poten- tial energy (remember: negative potential is where potential energy is HIGHEST for negative charges) but this energy gets directly converted into vibrations of the atoms in the wire. Since these vibrations are chaotic and uncoordinated, they appear as heat (an- other form of energy). Some small part of this heat is eventually converted to light, but most of it just makes the light bulb (and its surroundings) hotter. Finally the electron reaches the positive battery pole, at the lowest possible potential energy. To continue the journey (as it must to close the circuit), some other form of energy is needed to “pump” it back up to the negative pole. This energy is chemical binding energy – the battery com- ponents undergo a chemical reaction that convert some of the chemical energy stored in the battery into the necessary potential energy of the electron as it goes to the negative pole. Merry Christmas/Kwaanza/Hanukah/New Year
NOTE : TOTAL POINTS POSSIBLE FOR THE ENTIRE EXAM: 47. POINTS NEEDED
FOR A SCORE OF 100%: 40. ANY POINTS BEYOND THAT ARE EXTRA CREDIT!
