Explanation 3.10.1. Three Cars Redux.
Recall Exercise 3.4.3. Answer this question again. As part of your explanation, discuss how your answer, your reasoning, or your understanding has changed since you first thought about this task.
Section 3.10 Challenge - Laws of Motion
Subsection Explanation Tasks
Explanation 3.10.2. The Angled Block.
In the two situations depicted below, an angled block is at rest on a ramp. In each case, a hand pushes on the block with constant force. In Case A, the hand pushes on the upper horizontal surface of the block. In Case B, the hand pushes on the upper angled surface with a constant force of the same magnitude. In both cases, the block remains at rest on the ramp.
Part A: Is the magnitude of the net force on the block in Case B greater than, less than, or equal to the magnitude of the net force in Case A?
Part B: Is the magnitude of the frictional force exerted on the block by the ramp in Case B greater than, less than, or equal to the magnitude of the frictional force in Case A?
Subsection A*R*C*S Activities
Activity 3.10.3. Metacognition: Finding Similarities.
If you have not done so already, complete the following two A*R*C*S activities: Exercise 3.9.1 and Exercise 3.9.2.
In 2-3 written paragraphs, discuss the similarities and differences between these two activities. Consider both the physical contexts and the overarching strategies you used to approach each context.
For each A*R*C*S activity, you are expected to complete all of the steps in Figure 3.9.1. For your first several A*R*C*S activities, the tips include several helper pointers.
A*R*C*S 3.10.4. The Coach vs. the Student-Athletes.
The figure below shows a top-down view of a tug-of-war between a coach (in red on the left) and two teams of “student-athletes”. The coach can pull with a force of 1500 N, and the two teams together are just able to keep the rock connected to the ropes from beginning to accelerate. Determine the magnitude of the tension force provided by each of the two teams.
Tip 1.
Tip 2.
Tip 3.
Analyze and Represent: Sketch a free-body diagram for the situation. Think carefully about what reference frame you want to choose and break each force into components.
Calculate: Remember that your answer and work should be primarily symbolic. Choosing good symbols for both known and unknown quantities (including the angles!) can help support both your algebra and your sensemaking.
Sensemake: As part of your symbolic sensemaking (part 3c), try covariational reasoning for at least one of the three known quantities.
References References
[1]
Tug of War image inspired by teamwork by Lucas Helle from Noun Project (CC BY 3.0)
