Got Science Assessment
Video Modules 1 & 2
Understanding Kinetic Energy
Standards Alignments
These modules address Ohio Grade 9 Physical Sciences Curriculum Standards Indicator E.12:
Explain how an object's kinetic energy depends on its mass and its speed (KE = ½mv2).
Assessment & Questioning Strategies
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The level of the complexity of the performance expected from students will depend on their
prior preparation and achievement levels in the physical sciences and their aptitude. A series
of assessments will be provided here that start with the simplest tasks and progresses to the
more complex.
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Most often these assessments will be used after students have viewed the video and after the
instructor has performed demonstrations and at least some instruction and discussion. The
following questions can be posed to the entire class and students can be asked to respond and
then justify or explain their answers. The justification based on evidence and reasoning is the
most important part of students’ responses because this reveals the most about what students
actually understand. It also emphasizes the importance of evidence and reasoning for
developing scientific knowledge. When one student responds, without revealing whether the
response is correct, the instructor could ask another student whether ne/she agrees or disagrees
and to explain and justify his/her conclusion. Other students could also be asked for their
conclusion. Then the whole class could be asked to vote by raising their hands or through use
of student response devises. This strategy tends to encourage independent thinking and can
give a more accurate assessment of the level of achievement of more students in the class than
relying on the response of only one or two students for each question.
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Alternatively, various types of cooperative learning strategies could be used with these
assessment challenges such as posing the challenges to small groups (pairs, trios, or quartets)
of students with the charge that the members of each group should come to agreement on the
answers to these questions. These groups could then report to the whole class and the whole
class can then be challenged to reach agreement on the best responses and the evidence and
reasoning that justifies those responses as being the best.
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These questions could also be used as part of or adapted for a written exam to which each
student must respond individually and privately without consultation, or the questions could
be given to the students to complete as an in-class or homework exercise. Depending on how
and when these assessments are used in the classroom, the instructor may decide to modify the
questions or formats somewhat to fit the specific circumstances of the individual classroom.
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Assessment Challenges
1. Will increasing the mass of the car increase or decrease the kinetic energy? Will
increasing the car’s speed increase or decrease the kinetic energy?
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This is the simplest assessment just intended to determine whether students grasp the
direction of change. Students should, of course, respond that increasing the mass or
speed increases kinetic energy and vice versa.
2. Will doubling the mass increase the kinetic energy the same amount as doubling the
speed? Which will increase the kinetic energy more, increasing the mass or increasing the
speed?
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These questions will determine whether students comprehend that increases in speed will
result in a greater increase in kinetic energy compared to a comparable change in mass.
3. How much will the kinetic energy increase if the mass is doubled? If the speed is
doubled?
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Students who have mastered this standard should be able to predict that the kinetic
energy will double if the mass is doubled and the kinetic energy will quadruple (increase
by a factor of 4) if the speed is doubled. They should thus recognize and be able to
explain that increases in speed have a greater effect on kinetic energy increase than the
same relative magnitude increases in mass.
4. If the initial mass is 20 grams, how much will the kinetic energy change if the mass is
increased by 20 grams to a total mass of 40 grams while keeping the speed the same? If the
initial mass is 80 grams how much will the kinetic energy change if the mass is increased by
80 grams to a total mass of 160 grams while keeping the speed the same?
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These two questions are intended to assess whether students recognize that both of these
cases involve doubling the mass and thus both result in doubling the kinetic energy even
though there is greater increase of mass in the second case (80 grams increase)
compared to the first case (only 20 grams increase).
5. If the initial speed is 1 m/s, how much will the kinetic energy change if the speed is
increased by 1 m/s to a total speed of 2 m/s while keeping the mass the same? If the initial
speed is 4 m/s, how much will the kinetic energy change if the speed is increased by 4 m/s to
8 m/s while keeping the mass the same?
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Again, these two questions are intended to assess whether students recognize that both of
these cases involve doubling the speed and thus both result in quadrupling the kinetic
energy even though there is greater increase of speed in the second case compared to the
first case. Other variations can be used to further explore students’ understanding of this
mathematical relationship.
6. If the mass is 10 grams and the speed is 2 m/s, what is the kinetic energy?
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This question and variations of it using different magnitudes for grams and speed will
determine whether students can perform this calculation correctly. The values in this
question were chosen to make the calculation particularly easy; in this case KE =
1/2×10g×(2m/s)2 = 20 mJ. Students ability to perform this calculation with numbers that
cannot be as easily calculated without writing or using a calculator can further test this
ability but it should be possible to fully assess students’ ability with respect to this level of
achievement with just a few well designed problems. We do not recommend giving
students more than a few such problems since assigning too many problems of this type
are likely to dull most students interest once they have clearly mastered this skill level.
7. If the initial mass is 12 grams and the final mass is 18 grams, what is the relative change
in kinetic energy?
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KE1/KE2 = ½m1v12/ ½m2v22 = but since v is the same in both cases this simplifies to
KE1/KE2 = m1/m2 = 12g/18g = 2/3.
8. If the initial speed is 2 m/s and the final speed is 4 m/s what is the relative change in
kinetic energy?
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KE1/KE2 = ½m1v12/ ½m2v22 = but since m is the same in both cases this simplifies to
KE1/KE2 = v12/v22 = (2 m/s)2/(4 m/s)2 = 4/16 = 1/4.
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NOTE: These two questions will determine whether students can fully use the
mathematical relationship to derive relative change in kinetic energy. Many students mail
fail at this task unless they are given more guidance in deriving the mathematical
relationships that are needed for this type of solution and how to use those relationships.
The solutions shown here are just one way to answer this challenge. Again, these
questions can be modified by substituting different quantities. Indeed, the first such
questions can involve relatively simple mathematical relationships as for the questions
above that involve doubling the quantities. Then subsequent questions can gradually
increase the complexity of the relationships as students derive the insight they need to
answers these types of questions.
9. If a car with a mass of 4800 kg traveling at 10 m/s collides with a wall, what speed would
be needed for a 1200 kg car to experience the same degree of damage in the same type of
collision?
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This type of question is intended to determine whether students can derive yet another
variation in this mathematical relationship. There are several methods that could be used
to answer a question like this. One can compare the ratios but one has to also include the
square relationship of speed to kinetic energy. One way to answer this question is to
determine the kinetic energy of the first case = 4800 kg × (10 m/s)2 = 480,000 Joules.
Then one can solve for the speed in the second case by solving the algebraic equation:
480,000 Joules = 1200 kg X2; X = 20 m/s. One could also recognize that the mass is four
times smaller thus the speed would have to be 2 times greater to have equal kinetic
energy. A third solution would use ratios and “cross multiply” but one must take care
using this approach to include the square relationship of speed correctly. Variations on
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this type of problem could be used to further explore students understanding and ability
to derive variations of the mathematical relationship.
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NOTE: Other questions could also be developed that involve potential energy and its
conversion to kinetic energy as well as the reverse conversion but those questions are
beyond the scope of this curriculum standard so they will not be presented here.
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Got Science Student Worksheet
Video Modules 1 & 2
Understanding Kinetic
Energy
1. Will increasing the mass of the car increase or decrease the kinetic energy? Will
increasing the car’s speed increase or decrease the kinetic energy?
2. Will doubling the mass increase the kinetic energy the same amount as doubling the
speed? Which will increase the kinetic energy more, increasing the mass or
increasing the speed?
3. How much will the kinetic energy increase if the mass is doubled? If the speed is
doubled?
4. If the initial mass is 20 grams, how much will the kinetic energy change if the mass
is increased by 20 grams to a total mass of 40 grams while keeping the speed the
same? If the initial mass is 80 grams how much will the kinetic energy change if the
mass is increased by 80 grams to a total mass of 160 grams while keeping the speed
the same?
5. If the initial speed is 1 m/s, how much will the kinetic energy change if the speed is
increased by 1 m/s to a total speed of 2 m/s while keeping the mass the same? If the
initial speed is 4 m/s, how much will the kinetic energy change if the speed is
increased by 4 m/s to 8 m/s while keeping the mass the same?
6. If the mass is 10 grams and the speed is 2 m/s, what is the kinetic energy?
7. If the initial mass is 12 grams and the final mass is 18 grams, what is the relative
change in kinetic energy?
8. If the initial speed is 2 m/s and the final speed is 4 m/s what is the relative change in
kinetic energy?
9. If a car with a mass of 4800 kg traveling at 10 m/s collides with a wall, what speed
would be needed for a 1200 kg car to experience the same degree of damage in the
same type of collision?
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