Module: Objects and Motion
DCI: PS2.A (A) Forces and Motion – Each force acts on one
particular object and has both strength and a direction. An object at rest
typically has multiple forces acting on it, but they add to give zero net force
on the object. Forces that do not sum to zero can cause changes in the objects
speed or direction of motion.
DCI: PS2.A (B) Forces and Motion – The patterns of an object’s
motion in various situations can be observed and measured; when the past motion
exhibits a regular pattern, future motion can be predicted from it.
DCI: PS2.B (A) Types of Interactions – Objects in contact exert
forces on each other.
PE: 3-PS2-1 Plan and conduct an investigation to provide evidence
of the effects of balanced and unbalanced forces on the motion of an object.
PE: 3-PS2-2 Make observations and/or measurements of an object’s
motion to provide evidence that a pattern can be used to predict future motion.
[Clarification
Statement: Examples of motion with a predictable pattern could include a child
swinging in a swing, a ball rolling back and forth in a bowl, and two children
on a see-saw.] [Assessment Boundary: Assessment does not include technical
terms such as period and frequency.]
-Until one reads the "Clarification Statement, it is not obvious that the emphasis is on periodic motion. Only the word "pattern" in the very last statement even hits that we need to focus on periodic movement.
-Though the emphasis might be on periodic movement, questions about a body at rest (all the forces adding up to zero) and even motion in one direction (the result of unbalanced forces) seem to be fair game.
We can incorporate the verbs "plan and investigate" into a multiple choice test item by writing some semblance of an investigative design and asking students to either make a choice about the design or ask them what the investigation might be seeking to find out. We will definitely need graphics for this batch.
-Though the emphasis might be on periodic movement, questions about a body at rest (all the forces adding up to zero) and even motion in one direction (the result of unbalanced forces) seem to be fair game.
We can incorporate the verbs "plan and investigate" into a multiple choice test item by writing some semblance of an investigative design and asking students to either make a choice about the design or ask them what the investigation might be seeking to find out. We will definitely need graphics for this batch.
For PS2-2 - we can provide a graphic of some sort (perhaps the child swinging on a swing), and ask them to predict the future movement.
Possible Question Starters:
"Which of the following best describes the forces acting on a soccer ball which is resting on the ground?"
Correct answer = all of the forces acting on the ball are balanced
Incorrect answers = the force of the ground is less than the force of gravity, etc.
"Which of the following pictures below shows an example of unbalanced forces acting on an object?"
Four pictures - several showing an object at rest and one showing an object changing direction or accelerating [This may work better with short descriptions as it is notoriously difficult to illustrate an object in motion with a static image. - cjt]
"Students released a marble one one side of a glass bowl and observed and recorded its motion."
[data table
time (sec) location
0 Position 1
1 Position 2
2 Position 1
3 Position 2
The marble can be expected to be at position 1 at what time?
"Students released a marble one one side of a glass bowl and observed and recorded its motion."
[data table
time (sec) location
0 Position 1
1 Position 2
2 Position 1
3 Position 2
The marble can be expected to be at position 1 at what time?
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