Reflection: Checks for Understanding Manipulating Forces - Section 2: Student FBD Activity


Because this lesson involves both a time element and the chance to move cut-outs around, I find that this keeps the majority of students fully engaged.  As the timer runs downs, students are discussing the situation and moving the arrows around as they figure out what forces must be acting.

Most of the students get most of the first 9 questions correct.   They assess the motion of the box and correctly determine the forces that must be acting.  It helps that the actual cut outs only have two sizes, so they must know that if acceleration is involved, then their there is no restive force or they must use the bigger arrow.  

The questions where I see a lot of students struggle is with numbers 10 through 16.  Students routinely add forces where there are none or miss forces that must be included.  The student work example shows a typical case on question 12 where they want to include an applied force to the Voyager spacecraft as it moves through space.  Because it is moving with constant velocity, they know that the forces are balanced so they added a normal force.  But this is evidence of how difficult is it to overcome the mental model of constant motion requiring a constant pushing force that persists in many students minds.  

The last several problems do take a bit longer to complete as I explain why the answer are what they are and give students an opportunity to ask questions.

Doing this with multiple classes, I notice that there are always 3-4 students (usually the more more mathematically oriented) that find the pace of the Power Point to be too slow and they skip ahead on the answer sheet.  I don't mind students doing this.  In the future, I will differential and provide additional questions which are more challenging for these students.

  Checks for Understanding: Manipulating Forces Reflection
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Manipulating Forces

Unit 1: Forces in One Dimension
Lesson 3 of 11

Objective: Students use cut-out manipulatives to apply the concept of Newton's First Law to various situations.

Big Idea: An object changes its current motion when an unbalanced force acts it.

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3 teachers like this lesson
Manipulative Skills, Newton's First Law, Science, Physical Science, Newton's Laws, Newton's Second Law, Newton's Third Law, friction, physics, net force, constant velocity, free body diagram, inertia, kinematics, Forces
  50 minutes
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