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Announcements

Announcements. Homework for tomorrow… (Ch. 5, Probs. 1, 7, & 12) 4.4 a) v x = 4.7 m/s b ) v y = 2.7 m/s c ) (4.7 m/s ) ihat + (2.7 m/s ) jhat 4.14 b ) 3.2 km c ) 220° Office hours… M 3-4 pm TWR 9-10 am F 1-2 pm

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Announcements

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  1. Announcements • Homework for tomorrow… (Ch. 5, Probs. 1, 7, & 12) 4.4 a) vx = 4.7 m/sb) vy = 2.7 m/sc) (4.7 m/s) ihat + (2.7 m/s) jhat 4.14 b) 3.2 km c) 220° • Office hours… M 3-4 pm TWR 9-10 am F 1-2 pm • Tutorial Learning Center – Houston Hall 113 MWR 8 am-6 pm T 8 am-7 pm F 8 am-5 pm

  2. Chapter 5 Net Force and 2D Motion (Projectile Motion)

  3. Quiz Question 1 Suppose you are carrying a ball and running at constant speed, and wish to throw the ball and catch it as is comes back down. Should you: • throw the ball at an angle of about 45° above the horizontal and maintain the same speed. • throw the ball straight up in the air and slow down to catch it • throw the ball straight up in the air and maintain the same speed?

  4. Section 5.2:Projectile Motion The horizontal and vertical motions of a projectile are independent! The path of such a projectile can be found by combining its horizontal and vertical position components.

  5. Free Fall • All objects fall with a constant acceleration if… … they are near the Earth’s surface. … they are affected only by gravity. (i.e. air resistance is negligible)

  6. Projectile Motion continued… • The x- and y-directions of motion are independent of each other! • Motion in the x-direction is uniform motion • Motion in the y-direction is free fall

  7. Section 5.3:Analyzing Ideal Projectile Motion Projectile Motion • The object moves in both the x and y directions simultaneously • Object will follow the path of a parabola!

  8. Projectile Motion continued… • Simply apply our kinematic equations to each component of motion

  9. Projectile Motion continued.. • Thekinematic equations become…

  10. Projectile Motion continued… Notice that..

  11. Typical Homework/Exam Problem… Approach: 1. Break problem into x & y components 1 (2D) problem -> 2 (1D) problems 2. Use 1D Kinematic Equations

  12. i.e. problem Tom the cat is chasing Jerry the mouse across the surface of a table 1.5 m above the floor. Jerry steps out of the way at the last second, and Tom slides off the edge of the table at a speed of 5.0 m/s. Where will Tom strike the floor, and what velocity components will he have just before he hits?

  13. Quiz Question 2 As a projectile moves in its parabolic path, the velocity and acceleration vectors are perpendicular to each other • everywhere along the projectile’s path • at the peak of its path • nowhere along its path • not enough information is given

  14. i.e. problem An artillery shell is fired with an initial velocity of 300 m/s at 55.0º above the horizontal. To clear an avalanche, it explodes on a mountainside 42.0 s after firing. What are the x- and y-coordinates of the shell where it explodes, relative to the firing point?

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