Physics Chapter 3: 5-8: Projectile Motion

Homework

Reading Preparation
Key Equations
WebLecture
Study Activity
Chat Preparation Activities
Chapter Quiz
Lab Work

Reading Preparation

Text Reading: Giancoli, Physics - Principles with Applications, Chapter 3: Sections 5-8

Study Points

Section 5: Vectors at right angles do not affect one another. The horizontal components (unaffected by gravity) of a projectile's motion do not affect the vertical components (which are subject to gravitational acceleration), so we can analyze them separately.
Section 6: In working with projectile problems, always try to break the problem apart into vertical and horizontal components of motion (displacement, velocity, acceleration). Select your origin and frame of reference to make the math simple, and use it consistently. To get the final summary solution, add the horizontal and vertical vectors back together.
Section 7: Note that motion of a projectile is parabolic and described by the quadratic equation, so we can use the mathematical tools we know for quadratics to specific projectile situations.
Section 8: Velocity is measured based on a frame of reference. An observer on a roadside uses a different frame of reference (and sees a different velocity) than an observer in a moving vehicle. To compare velocities, we have to know the difference in the velocities of the frames of reference. An important law of physics is that as long as neither frame is accelerating, the laws of physics will be the same in both frames.

Key Equations

The Range Equation for Projectiles (where y = y₀) $R = \frac{{v_{0}}^{2} \sin 2 θ_{0}}{g}$

Note that when θ₀ = 45°, sin 2θ = sin 90° = 1, and has the maximum value possible for any θ, $R = \frac{{v_{0}}^{2}}{g}$

Projectile Motion is Parabolic $y = \frac{v_{y0}}{v_{x0}} x - (\frac{g}{2 {v_{x0}}^{2}}) x^{2}$

Web Lecture

Read the following weblecture before chat: Unit Vector notation

Study Activity

The HTML5 simulation below should run without an issue in your browser.

The "projectile motion" simulation allows you experiment with projectiles launched at different speeds and angles. Use the slide bar to adjust the initial speed. Grab the mouth of the cannon to tilt it to different angles. Use the red cannon button to fire the cannon and the eraser button to reset. See if you can find more than one combination to hit the bull's eye (three stars).

With the vectors panel, turn the different components on and off to identify the velocity and acceleration vectors involved, and watch how they change as the projectile ascends and descends. Are velocity and acceleration always in the same direction? Are acceleration and force always in the same direction?
We'll come back to this scenario to see how drag force affects projectile motion in the next chapter.

Physics simulations are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.

Chat Preparation Activities

Forum question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.

Chapter Quiz

Required: Complete the Mastery exercise with a passing score of 85% or better.
Go to the Moodle and take the quiz for this chat session to see how much you already know about astronomy!

Lab Work

If you want lab credit for this course, you must complete at least 18 labs; you may complete more if you are preparing for the AP exam.. One or more lab exercises are posted for each chapter as part of the homework assignment. We will be reviewing lab work at regular intervals, so do not get behind!

Lab Instructions: Complete Projectiles Lab

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Physics

Chapter 3: 5-8 Assignment