APP1 Unit 3: 2D Kinematics (1) 3 Nov 15

Transcription

1 APP1 Unit 3: 2D Kinematics (1) 3 Nov 15

2 2D Kinematics Projectile Motion

3 Assumptions: ignore air resistance g = 9.8 m/s/s downward ignore Earth s rotation If y-axis points upward, acceleration in x-direction is zero and acceleration in y-direction is -9.8 m/s/s. 2D Kinematics Projectile Motion Key Principle: Motion in the x- and y-directions can be considered independent; solve separately. The same kinematic equations you ve used apply just never mix your X s and Y s in the same equation.

4 2D Kinematics Projectile Motion The acceleration is independent of the direction of the velocity:

5 Zero Launch Angle Launch angle: direction of initial velocity with respect to horizontal Zero launch angle is a special case (helps us isolate what s going on as we master projectile motion)

6 Trajectory of Zero Launch Angle Projectile

7 Zero Launch Angle Projectile 12m Two spherical cows of uniform density jump off a 12m high cliff into the lake below. Cow 1 falls directly down without any horizontal velocity. Cow 2 jumps at zero launch angle with a velocity of + 4 m/s. Determine which cow contacts the water first.

8 Zero Launch Angle Projectile 1.2m Tom is chasing Jerry across the kitchen table. Jerry ducks out of the way (as he always does) and Tom slides off the table with a velocity of 5 m/s. Determine a) the Δt for Tom hitting the floor; b) Tom s Δx from te edge of the table; c) Tom s velocity when he hits the floor.

9 11/3 Practice For Wednesday: Read two-dimensional kinematics, Chapter 4, pp Solve: Conceptual exercises (p. 100): 11 Problems (p. 102): 13, 16, 17 Reading quizzes after today will not be announced. Be ready always.

10 Significant Assignment for the Weekend Read two-dimensional kinematics, Chapter 4, pp Solve: Conceptual questions (p. 99): 1 and 7 Conceptual exercises (p. 100): 1, 3, and 5 Problems (p. 101): 7, 9, 11 Poco Fiesta on TUESDAY, November 3d to demonstrate you accomplished your mission

11 APP1 Unit 3: 2D Kinematics (3) 6 Nov 15

12 Warm Up All are the same

13 No Saturday Morning Physics this Saturday

14 Case 2: Δy = 0: Δy = - 20m Our favorite break-neck skier, Calm E. Crazyhead, is testing his ski-jumping skills on the big platform at Iron Mountain, MI. He achieves an initial velocity of 15 m/s at an angle of 15- degrees from the horizontal. The landing area is 20 m below his point of launch. a. Determine the range he achieves from his point of launch. b. Determine the velocity with which he strikes the ground. May need to use quadratic equation

15 Projectile Motion Practicum Given the V o of a projectile launcher, and the Δy between the launcher and the floor, determine the range that the projectile will achieve. Prove it

16 11/6 Practice For Monday: Solve Problems (p ): 45, 59 Use PhET projectile motion simulation and examine: 1) Effect of projectile mass on range 2) Effect of projectile velocity on range 3) Effect of launch angle on range For additional explanation: Watch this video from Paul Hewitt that addresses projectile motion: Reading quizzes will not be announced. Be ready always. (p.s.: reading quizzes don t mean just reading )

17 APP1 Unit 3: 2D Kinematics (4) 9 Nov 15

18 Warm Up Incorrect: The ball that is thrown faster will also go higher. Faster things take less time to travel the same distance, but in this case the two balls don t travel the same distance. Both balls will have the same acceleration, 9.8 m/s/s downward, so both balls slow down at the same rate.

19 1 2D Motion poco Fiesta! 2 2D Motion grande Fiesta! 3 Energy poco Fiesta! 1 Begin Energy Unit 2 3

20 Projectile Motion Practice 1 A pilot is flying his SBD Dauntless dive bomber during the Battle of Midway (June 1944). His is making his diving run and releases his bomb in a dive angle of 45 O below the horizontal from an altitude of 550m above the target while flying at a rate of 50 m/s. (ignore air resistance and minimal lift provided by the bomb's stabilizing fins) a. Determine how long it will take his bomb to strike the target. b. Determine the range to target when he must release his bomb.

21 Projectile Motion Practice 2 Calm. E. Crazyhead is trying out motorcycle jumping. His plan is to jump a canyon that is 10m wide, and he ll use a ramp inclined at an angle of 15 degrees above the horizontal. Unfortunately, he never took physics and he doesn t know what velocity he must achieve to make this happen. Can you provide some wise counsel to him about this before he starts?

22 PMPM 01: I can represent the motion of a projectile using horizontal and vertical components of motion (velocity and acceleration). PMPM 02: I can represent the motion of a projectile using position-time, velocity-time, and acceleration-time graphs. PMPM 03: I can predict the future behavior of particles in projectile motion. PMPM 04: I can determine the x- and y-components of velocity for an object experiencing projectile motion. PMPM 05: I can solve problems involving objects experiencing projectile motion for horizontal launch angles. PMPM 06: I can solve problems involving objects experiencing projectile motion for general launch angles.

23 11/9 Practice For Tuesday: Review your notes and prior problems. Make up problems for yourself (or your friends) and solve them. Think through the principles of projectile motion what matters, what doesn t matter?

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