Cuesta College, San Luis Obispo, CA
Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.
The following questions were asked on reading textbook chapters and previewing presentations on free fall and vector components.
Selected/edited responses are given below.
Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"How to find the right variables for a problem by analyzing which parts of the information are given and which are not. I also understand how to determine which of the kinematic equations to use by determining which of the five variables needs to be found and how to rule out a variable that doesn't need to be found."
"Things can be thrown upwards (start with positive velocity), thrown downwards (start with negative velocity), or dropped (start with zero velocity)."
"During free fall, air resistance is neglected and the acceleration is nearly constant. Because acceleration is constant, we can use kinematic equations. Using a right triangle we are able to define sinθ cosθ and tanθ which helps us solve problems that involve angles. Scalars are numbers with magnitude such as time and volume while vectors are quantities with magnitude and direction such as displacement and velocity."
"I understand that an object can have a different vertical distance traveled than magnitude of vertical displacement. This is dependent on if the object is thrown straight in the air and then free falls, dropped into free fall, or thrown downward. I believe that the vertical displacement is equal to the distance if the object is dropped or thrown down, but the distance traveled is GREATER than the displacement if the object is thrown up."
"The fact that the only force acting on a ball falling down is gravity which has a constant acceleration is consistent with my understanding of physics. I also understand that vectors are determined by the x and y components in a triangle bringing us back to trigonometry.
Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"I was confused about how an object thrown or shot upwards can reach the same speed when it comes back down to its initial starting point as when it is thrown or shot downwards from its starting point."
"I found the homework problems a little bit confusing just because we haven't gone over many of those sorts of problems together. It would be very helpful to go over one of those specific problems in lecture."
"Trigonometry, but just a refresher would be useful.
Explain what assumptions are made about the amount of drag (air resistance) on an object said to be in free fall.
"We assume that drag forces are negligible."
"Air resistance is ignored."
Choose up to be the +y direction. The initial vertical velocity v0y has a __________ value.
For the boy, the vertical distance traveled is __________ the magnitude of the vertical displacement.
negative. *********** [11] zero. ********************************* [33] positive. *** [3] (Unsure/guessing/lost/help!) ** [2]
less than. *** [3] equal to. ************************************ [36] greater than. ******** [8] (Unsure/guessing/lost/help!) ** [2]
Choose up to be the +y direction. The initial vertical velocity v0y has a __________ value.
For the ball, the vertical distance traveled is __________ the magnitude of the vertical displacement.
negative. ************************* [25] zero. ********** [10] positive. ********* [9] (Unsure/guessing/lost/help!) ***** [5]
less than. ***** [5] equal to. **************************** [28] greater than. ****************** [13] (Unsure/guessing/lost/help!) *** [3]
Choose up to be the +y direction. The initial vertical velocity v0y has a __________ value.
For the hat, the vertical distance traveled is __________ the magnitude of the vertical displacement.
negative. **** [4] zero. ****** [6] positive. *********************************** [35] (Unsure/guessing/lost/help!) **** [4]
less than. ***** [5] equal to. *** [3] greater than. ************************************** [38] (Unsure/guessing/lost/help!) *** [3]
Mark the level of your exposure to trigonometry (triangles, unit circles, inverse functions, Pythagorean theorem):
None at all. * [1] Slight. *** [3] Some. ********** [10] A fair amount. ************************ [24] A lot. *********** [11]
Indicate the following trigonometric relations between angle θ, the opposite leg o, the adjacent leg a, and hypotenuse h for a right triangle. (Assume that the angle θ is in the first quadrant: 0° ≤ θ ≤ 90°.)
(Only correct responses shown.)
sin θ: (o/h) [92%]
cos θ: (a/h) [88%]
tan θ: (o/a) [88%]
hypotenuse h length: √(o2 + a2) [94%]
Describe what mnemonic device (if any) you use to memorize the right-triangle trigonometric relationships.
"Soh-cah-toa."
"Don't recall one."
"I've never heard one."
"I don't really use one."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"This is pretty cool. We are now moving into free fall which might start to make some things confusing and interesting when combining it with our horizontal motion knowledge."
"For the free fall examples above, would ground level be 0 or from when the ball left their hand?" (The convention used here is that we will always start at y = 0 at t = 0.)
"For all of the questions in this assignment, all of the initial velocities are zero? Because everything starts from not moving and is then thrown?" (If you throw a ball, it won't be in free fall (subject only to the force of gravity) until you let it go--so we can only start time t = 0 from the moment it was released with an initial velocity, as it leaves your hand.)
"Is there ever a setting where the free fall rules for falling objects don't apply?" (If air resistance (drag) is significant, then we can't say that acceleration is a constant value of 9.80 m/s2 downwards.)
"In terms of this class are we to automatically assume drag/air resistance doesn't matter or will it be noted?" (On the quizzes and midterms, it will always be stated whether or not air resistance is negligible.)
"The last time I used SOH CAH TOA was 10th grade, so it's a little fuzzy."
"Will we only be using trigonometry to solve problems? I like calculus but I get lost when it comes to applying it to physics for some reason." (We'll use trigonometry to break down diagonal vectors such that we can analyze horizontal and vertical motion separately for projectile motion.)
"Nothing to ask here. Looking forward to the lecture!"
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