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Ranking Task Sample I
For a ranking task, each item will have a number of situations as illustrated. Your task will be to rank the items in a
specific order. After ranking them you will be asked to identify the basis you used for the ranking and the reasoning
behind your choice. It is extremely important that you are careful to write out the proper ranking once you have
determined what basis you are going to use, i.e., make sure all of the situations are ranked in the proper order according to
your basis. The sample below shows how to rank items and what your explanation should be like. NOTE: Although the
procedure for working the item is correct, the particular answer, which was chosen at random from actual student
responses, may not be correct.
Example:
Shown below are eight cars that are moving along horizontal roads at specified speeds. Also given are the masses of the
cars. All of the cars are the same size and shape, but they are carrying loads with different masses. All of these cars are
going to be stopped by plowing into barrel barriers. All of the cars are going to be stopped in the same distance.
Rank these situations from greatest to least on the basis of the strength of the forces that will be needed to stop the cars in the
same distance. That is, put first the car on which the strongest force will have to be applied to stop it in x meters, and put last
the car on which the weakest force will be applied to stop the car in the same distance.
A
B
D
16 m/s
8 m/s
5 m/s
m = 1200 kg
m = 1000 kg
m = 1600 kg
m = 1500 kg
E
Greatest
C
12 m/s
F
G
H
9 m/s
12 m/s
5 m/s
10 m/s
m = 1200 kg
m = 1600 kg
m = 1500 kg
m = 1100 kg
1 B
2 AF
3
4 H
5 E
6 C
7 DG 8
Least
Or, all cars require the same force. ________
Please carefully explain your reasoning.
Since acceleration is the change in velocity divided by the change in time and all the changes in times are the same, then I
used the change in velocity.
How sure were you of your ranking? (circle one)
Basically Guessed
1
2
3
4
5
Sure
6
7
8
9
Very Sure
10
Notice in this example that two situations produced the same result for the ranking and that these were listed in the same
answer blank. Such a possibility exists for all items. In the same way, it is possible that all of the situations will give the
same result. If that occurs, and only if that occurs, the option of all equal, or all the same, should be chosen.
Full file at http://testbanksite.eu/E-and-M-Tipers-Electricity-and-Magnetism-Tasks-1st-Edition-Solution
Ranking Task Sample II
Each ranking task will have a number of situations, or variations of a situation, that have varying values for two or three
variables. Your task is to rank these variations on a specified basis. After ranking the items, you will be asked to explain
how you determined your ranking sequence and the reasoning behind the way you used the values of the variables to reach
your answer. An example of how to work the ranking tasks follows.
Example:
Shown below are six situations where a cart, which is initially moving to the right, has a force applied to it such that the
force will cause the cart to come to a stop. All of the carts have the same initial speed, but the masses of the carts vary, as do
the forces acting upon them.
Rank these situations, from greatest to least, on the basis of how long it will take each cart to stop.
A
B
60 N
C
48 N
48 N
60 g
40 g
60 g
D
E
F
60 N
75 g
40 N
40 N
50 g
40 g
Greatest 1___B___ 2___A___ 3___F____ 4___C __ 5___D____ 6____E____ Least Or,
all of these carts will require the same time to stop. _______
Please carefully explain your reasoning.
I think the time depends on the acceleration, so I divided the forces by the masses.
How sure were you of your ranking? (circle one)
Basically Guessed
1
2
3
4
5
Sure
6
7
8
9
Very Sure
10
Notice in this example that in one instance, two of the situations produced the same value of the ratio used to determine the
ranking, and that the letters for the ones that tied are circled showing they were ranked equally (A and F). In another
instance, three of the remaining situations have the same ranking and they are circled together (C and D and E), showing this
result. In the same way, it is possible that all of the arrangements will give the same result for a particular basis. If that occurs,
and only if that occurs, the option of all equal, or all the same, should be chosen.
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ELECTROSTATICS
RANKING TASKS (RT)
ET1-RT1: CHARGED INSULATING BLOCKS—CHARGE DENSITY
The block of insulating material shown at right has a volume Vo. An overall
charge Qo is spread evenly throughout the volume of the block so that the block
has a uniform charge density ρ o.
V o Qo
ρ
o
Six additional charged insulating blocks are shown below. For each block, the
volume is given as well as either the charge or the charge density.
2Vo
Vo
2Vo
2Vo
2Qo
Qo
2Qo
Block A
Block B
Block C
2Vo
ρ
Vo
2ρ
2ρ
o
Block D
o
o
Block E
Block F
Rank the charge densities of the six blocks.
Greatest 1 ___ AEF ____ 2 _______ 3 _______ 4 ___ BD ____ 5 _______ 6 ___ C ____ Least
OR, the charge density is the same for all six blocks. ____
OR, the ranking for the charge density cannot be determined. ____
Carefully explain your reasoning.
Charge density is defined as the ratio of total charge divided by volume, so you compute that for each
block if not already given.
How sure were you of your ranking? (circle one)
Basically Guessed
Sure
1
2
3
4
5
6
7
8
9
Very Sure
10
Full file at http://testbanksite.eu/E-and-M-Tipers-Electricity-and-Magnetism-Tasks-1st-Edition-Solution
ET1-RT2:
BREAKING A CHARGED INSULATING BLOCK—CHARGE DENSITY
A block of insulating material (labeled O in the diagram) with a width w, height h, and thickness t has a
positive charge +Qo distributed uniformly throughout its volume. The block is then broken into three
pieces, A, B, and C, as shown.
2w/3
A
O
w/3
B
h/3
C
2h/3
Rank the charge densities of the original block O, piece A, piece B, and piece C.
Greatest 1 _____ 2 _____ 3 _____ 4 _____ Least
OR, the charge density is the same for all four pieces. __ X __
OR, the ranking for the charge densities cannot be determined. ____
Carefully explain your reasoning.
The charge density is not going to change because each block will have a charge proportional to its
volume since the charge is uniformly distributed.
How sure were you of your ranking? (circle one)
Basically Guessed
Sure
1
2
3
4
5
6
7
8
9
Very Sure
10
Full file at http://testbanksite.eu/E-and-M-Tipers-Electricity-and-Magnetism-Tasks-1st-Edition-Solution
ET1-RT3: CHARGED INSULATING BLOCKS—CHARGE
The block of insulating material shown at right has a volume Vo. An overall
charge Qo is spread uniformly throughout the volume of the block so that the
block has a charge density ρ o.
V o Qo
ρ
o
Six additional charged insulating blocks are shown below. For each block, the volume is given as well as
either the charge or the charge density of the block.
2Vo
Vo
2Qo
Block A
2Vo
2Qo
Block B
2Vo
Qo
Block C
2Vo
ρ
Vo
o
Block D
2ρ
2ρ
o
o
Block E
Block F
Rank the overall charge of the six blocks.
Greatest 1 ___ F ____ 2 ___ ABDE ____ 3 _______ 4 _______ 5 _______ 6 ___ C ____ Least
OR, the charge is the same for all six blocks. ____
OR, the ranking for the charge cannot be determined. ____
Carefully explain your reasoning.
To determine the total charge for the blocks where it is not given we need to multiply the charge density by
the volume and then rank the blocks.