Errata for Motion AR

Student Reader, p. R4, middle:

• The components of the position of the ant should be given everywhere in "centimeters" not "meters". [EH, 06Jun04]

Student Reader, p. R9, top:

• The average velocity from t = 5.0s to t = 6.0s is +10cm/s, not −10cm/s. [AW, 14Jan04]

Many thanks to Andrew Wertz of Littlestown HS in Littlestown, PA, and Ed Haley of E.C.O.S. in Springfield, MA, who found these mistakes.

Errata for Motion TG

Activity 4, p. 22, question P8, part (a) answer

• Add graph D to the list of answers, i.e., "Graphs C, D, and E represent objects that are speeding up."

Activity 8, p. 39, "Link to Reader"

• Change the ending page of the reading assignment to R9, i.e., "Students may read pages R8-9 (the beginning of section 1.4, Velocity) after finishing Activity 9."

Activity 9, p. 45, "Link to Reader"

• Change the ending page of the reading assignment to R9, i.e., "Students may read pages R8-9 (the beginning of section 1.4, Velocity) after finishing this activity."

Activity 9, p. 46, "Probing for Student Understanding", question P3

• In parts (a) and (c), change the units to cm/s, i.e., "P3. (a) Which object (in part A) reaches a velocity of 1cm/s first? (b) When does this occur? (c) Which object reaches a speed of 1cm/s first? (d) When does this occur?"

Activity 12, p. 65, question A4 answer, bullet 1

• Change wording to "Students might plot speed vs. time instead of velocity vs. time (as shown below on the left). In addition, some students might not realize that the speed goes to zero between strobes 4 and 5 (as shown below on the right)."

Activity 12, p. 68, question B4 answer

• Change answer to "after t = 0.45s".
• Add third bullet, "• By exaggerating the curvature of the graph between #4 and #5, you can see that the marble is at the 1m mark just after the midpoint in time."

Activity 13, p. 76, question P1 answer

• In part (a), at t = 1½s, object X is at x = 7½cm.

Activity 14, p. 79

• question A2 answer, bullet 1, "Object J has the largest displacement..."
• question A4 answer, bullet 1, "Students might pick only object J, because object I..."
• question A4 answer, bullet 2, "Students might pick only object I..."
• question A6 answer, "... which would correspond to J"
• question A6 answer, bullet 1, "Students might pick object I because the curves for objects E and I look the same."

Activity 15, p. 86, question P1 answer

• The answers to parts (a) and (b) are reversed.

Activity 16, p. 91, question C3 answer

• Modify paragraph 2: "Yes, this answer agrees..."
• Fix bullet 1: "Students might have gotten question B2 wrong."

Activity 17, p. 96, question A5 answer

• Add to the end of paragraph 1, "At 20km/h, the plane travels about 5½km before losing contact with the car."
• Add to the end of bullet 1, "i.e., after the plane has traveled 20km".

Activity 19, p. 107, question P4 answer

• The speed is only 1 grid/s, i.e., the answer should read, "... the average velocity is +1 grid/s —or— 1 grid/s, to the right between 2s and 6s."

Activity 23, p. 131, question P8 answer

• Add bullet, "• See table of values for P1 above."

Activity 24, p. 137, question B1 answer, bullet 4

• Change A2-A4 to B2-B4, i.e., "Students do not need to make precise calculations to answer questions B2-B4."

Activity 25, p. 145, question A2 answer

• In part (i), the Total Area (i.e., column 4) should be 292.5 m.

Activity 27, p. 163

• question R2 answer is really only the first half of the answer to R2.

• question R3 answer is really the second half of the answer to R2.

• question R4 answer is really the answer to R3.

• question R5 answer is really the answer to R4.

Many thanks to Lonnie Grimes of Oakmont High School in Roseville, CA, who found almost all of these mistakes.

Errata for Interactions AR

Activity 37, p. 146, "Explanation of Activity and Examples":

• The page number indicating where to find the map (of King's Court) should be "143", not 134.

Many thanks to Patrick Diehl of Ashley Hall School in Charleston, SC, who found this mistake.

Errata for Interactions TG

Activity 36, p. 216, question A4 answer

• Quadrant (column 1) should be "2 only", angle relative to horizontal (column 2) should be "27°", and angle relative to East axis (column 3) should be "153°".

Activity 36, p. 217

• Answer to question B2 should be: 580m @ 149°.
• Answer to question B3 should be: 500m @ 307°.
• Answer to question B3, bullet 1: replace -37° with -53°.

Activity 37, p.222, "Suggested Points for Class Discussion", bullet 2

• The word 'needs' should be 'need', i.e., "... both the origin and the orientation of the coordinate frame need to be specified..."

Activity 38, p. 227, question A5 answer

• All the answers for vector V are wrong. There should be a minus sign in front of each term, and the length of the vector is 4.24cm. So, the x-component of V can be written either -(4.24cm) cos(45°) or -(4.24cm) sin(45°), and the y-component of V can be written either -(4.24cm) sin(45°) or -(4.24cm) cos(45°).

Activity 38, p. 229, question B5 answer, bullet 2

• Change B3 to B2, i.e., "Students might use a rotated coordinate system (as in B2)."

Activity 42, p. 258, question B1 answer, bullet 1

• Rephrase third sentence to read, "This is the only situation in this part for which buoyancy is considered relevant."

Activity 44, p. 267, "Probing for Student Understanding"

• Change part (b) of question P3 to read, "In part B, how would the readings on scales A, B, and D change if scale C were removed?"

Activity 45, p. 280

• In the answer to question I7, add object E to the list, i.e., "Only objects A, B, D, and E must have friction forces exerted on them."
• The answer to question R3 is missing. It should read, "The objects considered in situations A3, A6, and B3 could be accelerating. For the rest, the object has a constant velocity.
• There are no comments for R3. They are,
• "Students might not include A3, perhaps because they think the ball is not accelerating at the top of its trajectory."
• "Students might include B1, perhaps because the book is accelerating. But the object being considered is the table, which is not accelerating."
• "Students might not include B3, perhaps because they think that the ball is at rest when it is touching the wall."
• "At this point in the course, students are not expected to know the relationship between force and acceleration. Students should be encouraged to determine which objects definitely have no acceleration. The rest can be considered to possibly be accelerating."
• The answer for question R4 is missing. It should read, "(Students indicate any forces other than the seven introduced here that they have heard of. They then indicate if any of these other forces behave like any of the forces introduced here."

Activity 45, p. 281

• The answer to question P5 is wrong. It should read, "If the spring was compressed rather than stretched, then the strings would be angled inward, rather than outward. In other words, object G would be hanging to the left of where its string is attached to C, and object H would be hanging to the right of where its string is attached to C."
• The comment for the answer to question P5 does not fit any longer. It should read, "Students might not think it is possible for the spring to remain compressed between objects G and H."

Activity 46, p. 284, "(More Ways of) Probing for Student Understanding"

• Question P6 is question P4.
• Question P7 is question P5.
• Question P8 is question P6.

Activity 47, p. 294, question R2 answer

• Change 'part B' to 'part A', i.e., "In situation C of part A, the normal force..."

Activity 48, p. 297, "Suggested Points for Class Discussion", bullet 2, last sentence

• The word 'a' should be 'at', i.e., "(Thus, one can be at rest; the friction is still kinetic.)"

Activity 49, p. 307

• The first entry in the table is not the beginning of the answer to question A4, but a continuation of the answer to question A3.
• The answer to question A4 begins with gravitation.
• There is a force missing from the answer to question A4. The force (i.e., column 1) is "kinetic friction." The way it will be determined (column 2) is "Multiply the normal force by the coefficient of kinetic friction. Direction is opposite the motion of _m_₁." The magnitude & direction (column 3) is "(NA)." Comment is "• We do not actually know the normal force, so we cannot determine the force of kinetic friction. However, students might think that they know the normal force using common sense."

Activity 49, p. 308, question R1 answer

• The second bullet for air resistance is wrong. It should read, "At very small speeds, the force law is closer to Bv.

Activity 51, p. 324

• The answer to question B1, part (a) is wrong. The x-component of F_{_N_,left} should be F__{_N},left.
• The answer to question B1, part (b) is wrong. The x-component of F_{_N_,right} should be -F__{_N},right.
• The answer to question B2, part (c) is confusing. Vectors F_{_g_1}, F_{_N_2}, and F_{_T_2} are not part of the answer. They are simply the other vectors in the situation, which are included because their components are known.
• The answer to question B2, part (d) is wrong. The x-component of F_{_g_2} should be -F__{_g_2} cos 60°, and its _y-component should be -_F__{_g_2} sin 60°.
• The word "the" should be removed from the second line of the last bullet for the answer to question B2, i.e., "Even if we notate the magnitude of both tension forces as..."

Activity 54, p. 350, question P9 answer

• Change "velocity" to "velocities", i.e., "(a,b) The forces... Kinetic Friction, which depends on the relative velocities of the objects in contact, and..."

Activity 55, p. 357, question A5 answer

• In the table showing the time intervals during which the ball is accelerating, change '4.9s' to '4.8s', i.e., the time interval corresponding to the 2nd time the ball is rolling across the felt should be [4.8s, 6.5s].
• In the table showing time intervals during which its velocity is constant (it's part of the 4th bullet of the answer to question A5), change '4.9s' to '4.8s', i.e., the third time interval during which the ball is rolling at constant velocity is [3.51s, 4.8s].

Activity 56, p. 370, question C4 answer, bullet 3

• Change 'any' to 'a', i.e., "Students might not perceive that there is a net force on them when they walk in a circle."

Activity 58, p. 384, question A2, part (c) answer

• Of the three free-body diagrams, the one on the left is for the skydiver, the one in the middle is for the parachute, and the one on the right is for the Earth.

Activity 58, p. 386, question B4 answer

• Add to the end of the answer to part (b): "But perhaps not as much faster and farther as before, assuming for example that she does not push as hard as her father did before."
• Add a bullet: "• In other words, her speed might be smaller than it was before, but it is always larger than her father's."

Activity 58, p. 387, question R1 answer, bullet 1

• Change to "The action-reaction pair has five features: exerted by different objects, exerted on different objects, same type (normal, gravitational, etc.), same magnitude, and opposite direction."

Activity 59, p. 389, "Suggestions for Classroom Use"

• Change bullet 2 to: "Focus students' attention on learning the answers and explanations to two questions using the following group structure: Divide the class into teams of 3 or 4 students each. Assign each team 2 questions from the same part, or put slips of paper with the numbers of 2 questions into a bowl and have teams choose. Tell students that each of them will be asked to write out the explanation to one of the questions, and that each student's grade will depend in part on how well the other team members do. As the teams are working, decide which explanation each student will provide. When the working time is complete, give students their assignments, to be done either during or after class. When grading explanations, give half credit for each individual's contribution and half credit for the contributions of the rest of the team. In other words, half of each student's grade will depend on his/her individual explanation, and the other half will depend on his/her team's explanations.
• Insert between bullets 2 and 3: "• For small classes with only a few teams, do parts B and D first, then repeat with parts C and E."
• Add bullet: "• As a class, compare answers and discuss areas of disagreement."

Activity 59, p. 391, question A4 answer

• Change 'rope 1' to 'rope 2', i.e., "... then the tension in rope 2 is larger in case II than in case I."

Activity 59, p. 392, question C2 answer

• Add bullet: "• Students might think that the velocity is larger because the net force is larger."

Activity 60, p. 402, question R2, part (a) answer

• Remove 'of the', i.e., "The mass is much larger for the car."

Many thanks to Lonnie Grimes of Oakmont High School in Roseville, CA, who found almost all of these mistakes.

Errata for Conservation Laws TG

Activity 74, p. 513, question B3, part (c) answer

• In the second paragraph, the area of each 'box' is wrong. It should be 0.01N-s, i.e., "... and each box has an area of (2N) x (0.005s) = 0.01N-s..."

Activity 76, p. 529, question A3 answer

• The parts are not labeled, i.e., the "(a)", "(b)", and "(c)" labels are missing.

Activity 76, p. 532

• The answers and comments to questions R1, R2, and R3 are missing.
• The answer for R1 is, "Total momentum is conserved for situations A3 and A6. It is zero initially, and remains the same throughout the time interval specified. Total momentum is approximately conserved for situation A1, because the impulse delivered to the system by gravitation is small during the explosion. At least one component of the total momentum is conserved for the other 5 situations. We define the x-direction to be the horizontal in the plane of the page (i.e., to the right), the y-direction to be the vertical, and the z-direction to be the horizontal perpendicular to the plane of the page (i.e., directly toward you). In situations A2, A4, and A7, the net external force is in the y-direction, so total momentum is conserved in the x- and z-directions. In situation A5, the net external force has y- and z-components, so momentum is conserved only in the x-direction."
• The comments for R1 are:
  • Students might think that momentum is not conserved in situation A6, because the wheel is slowing down.
  • Students might consider only the ball in A3, rather than the Earth-ball system.
  • In situation A3, students might not ignore the gravitational forces exerted on the Earth-ball system by the Sun, the Moon, and the planets.
  • Students might not recognize that the total momentum of the Earth-ball system is staying the same during the motion of the ball.
  • Students might only consider two directions, i.e., the x- and y-directions.
  • In situation A5, we are assuming that the bow string exerts a force on the arrow in the yz-plane.
  • Students might think that momentum is not conserved in any direction in situation A7, because the ball's are going in all directions.
• The answer for R2 is, "In situations A3 and A6, all forces are internal; the net force on each system is zero."
• The comments for R2 are:
  • If students do not have the correct set of situations here, they are likely to generalize improperly.
  • Students might not realize that in A3 they are expected to ignore the forces exerted by the Sun, the Moon, and the other planets.
  • Students might not realize that in A6 the net force on the wheel is zero, because it is slowing down.
• The answer to R3 is, "For those situations in which momentum is not conserved, there are external forces on the specified system. In each case, the direction of the change in momentum is the same as the direction of the net external force. In order to always conserve momentum, it is necessary to choose a system large enough so that there are no external forces on it. If we include the Earth in each system and ignore the gravitational forces exerted by the Sun, the Moon, and the planets, then momentum is conserved in all the situations."
• (There are no comments for R3 at this time.)

Activity 83, p. 584, question A1 answer

• The explanation (column 5) should read, "Monkey exerts F__{_N_1} and _F_fs. Whatever is holding up the rope exerts _F__{_N_2} (assuming, e.g., that the rope is tied to a hook in the ceiling). The displacement of the rope is zero."

Activity 87, p. 616, "Anticipated Difficulties for Students", bullet 7 (i.e., last bullet)

• The 'clay' should be a 'cart', i.e., "Analyzing the cart in situation R3... because the work done on the cart is done..."

Activity 87, p. 618, "Providing Support to Ensure Student Progress", bullet 6 (i.e., next to last bullet)

• Change to: "In situation R3, focus students attention on forces that are applied through a displacement, such as forces internal to the spring, rather than forces that are applied through zero displacement, such as the normal force exerted by the wall."

Activity 87, p. 620, question A3(b) answer

• The explanation is wrong, because we do not know how to calculate the work done by friction, as described in the Reader. Therefore, students are expected simply to use common sense to try to answer this question. Later, the explanation will be that there is a loss of energy from the macroscopic realm to the microscopic realm, which means that the speed must be smaller after hitting the spring than before.

Activity 87, p. 620, question A3(b) bullet

• The comment is inappropriate for the same reason that the explanation is inappropriate, that is we do not know how to calculate the work done by friction, as described in the Reader. It should read, "The work done by the friction force on the cart cannot be calculated or even estimated. Further, knowing its value would be of no consequence here, because all of the macroscopic kinetic energy lost by the cart becomes microscopic energy of the cart. In other words, the forces are internal to the cart, so the energy remains with the cart. However, at this point in the course, students are not expected to be able to make this distinction between macroscopic and microscopic energy."

Many thanks to Lonnie Grimes of Oakmont High School in Roseville, CA, who found almost all of these mistakes.

Errata for Advanced Topics AR

The following mistakes are in the first 3 printings of Vol. 4·AT / Activities & Reader. If you have a 4th printing or higher, they have been fixed. Please check the copyright page (page iv) to see which printing, or mixture of printings, you have.

Contents, p. v

• The correct title of Activity AT·13 is "Exploring Relative Motion in One and Two Dimensions".

Activity AT·4, p. 13, "Prior Experience/Knowledge Needed"

• The label of the first equation should read: tangential component of acceleration. The change in speed can be negative, and when it is, the direction of the tangential component of acceleration is opposite the direction of motion. And when the change of speed is positive, this component is in the direction of motion.

Activity AT·8, p. 30, question A3

• In the description of the situation, the speed of the marble three seconds later should be "80cm/s", not "79cm/s".

Activity AT·8, p. 31, question B2

• In the description of the situation, the second sentence should begin: "One second later..."

Activity AT·8, p. 31, question B3

• In the description of the situation, the time at which the toy car stops near the top of the incline should be "t = 0.58s", not "t = 1.8s".
• The fourth question in part (d) should be: What is the car's position and velocity at "t = 0.68s", not "t = 2s".

Activity AT·11, p. 44, question A1

• In the description of the situation, the initial speed of the puck should be "250cm/s", not "25cm/s".

Activity AT·17, p. 69, questions B1 & B2

• A car traveling at 29m/s is moving at "65mi/h", not "60mi/h". This mistake occurs twice in question B1 and once in question B2.

Activity AT·17, p. 69, question B3

• The diagram of situation A is not consistent with what is happening. In particular, there is not enough string left hanging to allow the wheel to spin as many times as it needs before stopping. The following diagram replaces the one accompanying the description. Right-click or command-click and choose “Open image in new window” (or equivalent) to see a full-sized version. Print that version at 100% for a transparency, or at 33% to replace the figure in students’ books. Also note that the diagram on the answer sheet is the Teacher's Guide is the same as that shown below. Finally, the angle of the incline in situation B has been made more shallow to be consistent with the additional changes listed below.
• Many of the values for the given information should be changed. The initial speed of the wheel is now 1rev/s, and it is slowing down at a rate of ¼rev/s². The ball is now a marble, and it is rolling up the incline at 4m/s and slowing down at a rate of 1m/s². (Changes shown in bold type.)
• The question for part (b) should read: "Write an expression for the position of the marble..." (Change shown in bold type.)

Activity AT·18, p. 73, question A5

• In part (b), when the car speeds up, its speed in miles per hour should be "65mi/h", not "60mi/h". In other words, 29m/s = 65mi/h.

Activity AT·21, p. 86, question R4

• The "second" part (b) should be part (c).
• Part (c) should be part (d).

Errata for Complex Systems AR

The following mistakes are in the first printing of Vol. 4•CS / Activities & Reader. If you have a 2nd printing or higher, they have been fixed. Please check the copyright page (page iv) to see which printing, or mixture of printings, you have.

Activity CS•3, p. 13, question A2(c)

• The mass of oil (fluid X) should be "16" (grams), not "18".

Activity CS•11, p. 50, property #4 of idealized fluids (at the very bottom of the page)

• The middle of the sentence should read: "... which means that both the pressure and speed are constant...".

Activity CS•11, p. 51, "Explanation of Activity"

• The mass of 10cm³ of oil should be "8g", not "9g".

Activity CS•11, p. 51, figure for problem A3

• The following figure should make it clearer to students what is going on here, i.e., the direction in which the glass tube is rotated so that it "rests on its side" in part (a). Right-click or command-click and choose "Open image in new window" (or equivalent) to see a full-sized version. Print that version at 100% for a transparency, or at 33% to replace the figure in students' books. (The answer sheet in the Complex Systems TG already has the corrected figure.)

Activity CS•12, p. 53, "Purpose and Expected Outcome"

• The last sentence should begin: "When you find a system to which you cannot apply..." (Change shown in bold type.)

Activity CS•22, p. 106, question A2

• Part (a) should read: "Which state(s) has the highest temperature? Explain."
• Part (b) should read: "Which state(s) has the lowest temperature? Explain." (Changes shown in bold type.)

Activity CS•26, p. 127, description for part B

• The springs being studied in this part of the activity are said to be "relaxed". This word should be omitted. Instead, the springs should be considered to have zero or very small relaxed length. The need for this change is that when the springs are relaxed initially, the balls attached to them in situation B1 would tend to move left and right as well as up and down, which is unnecessarily complicated. By making the relaxed length very small, the motion of the balls (in B1) becomes purely transverse, i.e., up and down. Note that this change affects only the results of B1.

Activity CS•30, p. 151, questions D3 and D4

• The question in D3 should read: "Will the wave form on the lighter spring move faster or slower than the original wave form on the heavier spring?"
• The question in D4 should begin: "Will the wave form on the lighter spring..." (Changes shown in bold type.)

Reader/Chapter 1: Fluids, p. R18, table showing speeds of water outside holes

• The list of speeds in the last column are wrong. The correct table is shown below. (Right-click or command-click and choose "Open image in new window" or equivalent to see a full-sized version, then print at 50% to replace in student books.)

Reader/Chapter 1: Fluids, p. R19, table showing speeds of water outside holes and where the water lands

• The list of speeds in the third column and the list of where the water lands in the last column are wrong. The correct table is shown below. (Right-click or command-click and choose "Open image in new window" or equivalent to see a full-sized version, then print at 50% to replace in student books.)

Many thanks to Prof. Josip Slisko of the Faculty of Physical and Mathematical Sciences at the Benemerita Public University in Puebla, Mexico, who found many of these mistakes.