1. In this chapter we will learn about the kinematics (displacement, velocity, acceleration) of a particle in two or three dimensions. Projectile motion Relative motion Chapter 4, part 2: Reading assignment: Chapter 5.1-5.4 Homework 7: (due Monday, Sept. 12, 2005): Chapter 5: Q15, 1, 11, 18, 21, 29

2. Projectile motion Two assumptions: 1.Free-fall acceleration g is _____________. 2.Air resistance is ________________. - The path of a projectile is a ________________ (derivation: see book). - Projectile leaves origin with an initial velocity of v i. - Projectile is launched at an angle  i - Velocity vector changes in _____________ and _______________. - Acceleration in y-direction (vertical) is _____________. - Acceleration in x-direction (horizontal) is ___________.

3. Acceleration in x-direction is 0. Acceleration in y-direction is g. (Constant ______________)(Constant __________________) Projectile motion of motion in x-direction and motion in y-direction The horizontal motion and vertical motion are _______________ of each other; that is, neither motion affects the other.

4. Simultaneous fall demo Which ball will hit the ground first? Straight drop Straight out Both released at the same time

5. A battleship simultaneously fires two shells at enemy ships. If the shells follow the parabolic trajectories shown, which ship gets hit first? 1) A. 2) B. 3) Both hit at the same time. 4) Need more information.

6. Hitting the bull’s eye. How’s that? Demo.

7. A rifle is aimed horizontally at a target 30 m away. The bullet hits the target 1.9 cm below the aiming point. (a)What is the bullets time of flight (b)What is the bullets speed as it emerges from the rifle? Black board example 4.2

8. A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 8.00 m/s at an angle of 20° below the horizontal. It strikes the ground 3.00 s later. (a)How far horizontally from the base of the building does the ball strike the ground? (b)Find the height from which the ball was thrown. (c)How long does it take the ball to reach a point 10 m below the level of launching? Black board example 4.3 x y 

9. Just to re-iterate: