## 20120912

### Online reading assignment: projectile motion, forces/interactions

Physics 205A, fall semester 2012
Cuesta College, San Luis Obispo, CA

Students have a 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 a presentation on projectile motion and forces/interactions.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
The demonstration in the book and the video about the two balls, one being dropped and one being shot out at the same time, because I would not have guessed for both balls to land at the exact same time. But after reading and thinking about it, it makes perfect sense."

"The horizontal velocity of a projectile does not change while it is in flight."
Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I always thought bigger objects as in mass had a greater free fall acceleration, but it's the same as small objects."

"Forces in general."
Explain what assumptions are made about the horizontal motion of an object experiencing ideal projectile motion.
"There is no air resistance on the object."

"Gravity accelerates objects downwards but does not affect horizontal motion."
Describe a situation with a negative (starting) angle of elevation for projectile motion.
"Shooting down from the top of a cliff, your angle of elevation is below the horizontal plane."

"A six-foot tall man is standing and throws a baseball at a pineapple which is two meters in front of him on the ground. The ground is not slanted."
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Are the labs going to get harder? The first two have been very easy." (Future labs may have more than one independent parameter to be investigated, and/or non-linear dependencies between independent and dependent parameters. Also more challenging challenge activities.)

"Could you please go over a couple sample 'quiz-like' questions in class tomorrow, to gear us up for Monday's quiz? : )" (Go through last semester's quiz and discussion. You can e-mail me about the questions on the archived quiz or other topics up until 10:00 PM the night before the quiz, and I will attempt to respond to you sometime later that night (or very early that morning).)