Author Archives: Automated Transfer Script

A2L Item 262

Goal: Hone the concept of a collision

Source: CT151.2S02-43

A cart
of mass m is moving with speed v. Is it possible for the kinetic energy
or the momentum to be larger after a collision?

  1. No; it is impossible
  2. Yes; the kinetic energy can be larger
  3. Yes; the momentum can be larger
  4. Yes; both can be larger

Commentary:

Answer

(4) Many students get fixated on the idea that all collisions are head
on and cause the object to lose energy and momentum.

A2L Item 263

Goal: Reason regarding interactions

Source: CT151.2S02-43

A
cart of mass 2m collides and sticks to a cart of mass m that is
initially at rest. Which cart exerts the larger force on the other?

  1. m
  2. 2m
  3. Both exert the same force
  4. Cannot be determined

Commentary:

Answer

(3) Yet another instance of Newton’s Third Law. Some students still
stumble because they the question considers the object exerting the
larger force as opposed to the one having the larger force applied to
it.

A2L Item 260

Goal: Interrelate representations of kinematical quantities

Source: CT151.2-10

An object’s motion is described by the graph above. The displacement
of the object during the entire 16 seconds is most nearly…

  1. 200 meters
  2. 250 meters
  3. 300 meters
  4. 350 meters
  5. 400 meters
  6. 450 meters
  7. Cannot be determined

Commentary:

Answer

(7) Students have difficulty reading graphs and finding areas.

A2L Item 261

Goal: Recognize a lack of information

Source: CT151.2S02-24

Consider the situations at right. Let m < M. Which spring has
the largest spring constant?

  1. A
  2. B
  3. C
  4. A and B are equal
  5. A and C are equal
  6. B and C are equal
  7. All of them have the same spring constant
  8. Cannot be determined

Commentary:

Answer

(8) The objective of this question is to reveal what students are
assuming about the springs. The reasoning behind any incorrect answer
should be thoroughly discussed.

A2L Item 258

Goal: Hone the concept of average velocity

Source: CTtil2;12;02

While traveling from Boston to Hartford, Person A drives at a constant
speed of 55 mph for the entire trip. Person B drives at 65 mph for half
the trip and then drives 45 mph for the second half of the trip. When
would B arrive in Hartford relative to A?

  1. B arrives before A.
  2. B arrives at the same time as A.
  3. B arrives after A.
  4. Not enough information.

Commentary:

Answer

(3) Many students are inclined to average the speeds and conclude that
they arrive at the same time. It is often useful to compare this
situation to the one in which time is halved.

A2L Item 259

Goal: Interrelate representations of kinematical quantities

Source: CT151.2-8

An object’s motion is described by the graph above. The position of the
object at t = 9 seconds is most nearly…

  1. 0 meters
  2. 200 meters
  3. 300 meters
  4. 400 meters
  5. 500 meters
  6. Cannot be determined

Commentary:

Answer

(6) This problem is primarily to determine if students appreciate the
information available from a graph. Many students will determine the
displacement forgetting that the initial position is unknown.

A2L Item 256

Goal: Hone the vector nature of the electric field

Source: CTQ283-6

Four charges are positioned as
shown. What is the direction of the electrical field at the origin?

  1. Along i or in the +x direction
  2. Along -i or in the -x direction
  3. Along j or in the +y direction
  4. Along -j or in the -y direction
  5. Along some other direction
  6. E=0 at the origin

Commentary:

Answer

(6) Difficulty with this question usually indicates that students are
not familiar with vectors. Good follow up question: ask whether it
matters if the charges are along a 45 degree line.

A2L Item 257

Goal: Hone the vector nature of the electric field

Source: CTQ283-7

Four
charges are positioned as shown. What is the direction of the
electrical field at the origin?

  1. Along i or in the +x direction
  2. Along -j or in the -y direction
  3. Along j or in the +y direction
  4. Along -i or in the -x direction
  5. Along some other direction
  6. E=0 at the origin

Commentary:

Answer

(3) Difficulty with this question indicates that students do not know
how the direction of the electric field relates to the sign of the
charge.