Projectile Motion 20201028 By Mr NGAN HON SHING

Projectile Motion 2020/10/28 By Mr. NGAN HON SHING 1

Simple Projectile Motion n n Consider a ball is thrown vertically upwards at 10 ms 1. Calculate the max. height it reached and the time of flight. 2020/10/28 By Mr. NGAN HON SHING 2

Max. Height n n Given u=10; v=0; a=-10. Find s (taking upward direction as +ve) By v 2 – u 2 = 2 as 0 – 100 = 2(-10)s s = 5 m 2020/10/28 By Mr. NGAN HON SHING 3

Time of flight n n Given u=10; a=-10; s=0. Find t. By s=ut+0. 5 at 2 0 = 10 t – 5 t 2= t(10 – 5 t) t = 0 (rejected) or 2 s 2020/10/28 By Mr. NGAN HON SHING 4

What’s happen in the following case? n n n If a boy throws a ball vertically upwards in a moving train, what is the motion of the ball? To the boy in train, it’s still a vertical motion. To an observer outside the train, it is a projectile motion. The ball is moving up and down, but it also moves horizontally. 2020/10/28 By Mr. NGAN HON SHING 5

Example: Dropping bomb ∵constant horizontal speed => same horizontal distance Vertical motion and horizontal motion are independent. Same Vertical Level 2020/10/28 By Mr. NGAN HON SHING 6

Projectile motion u uy=u sin The vertical and horizontal motions are independent. uy=u sin u ux=u cos It can be resolved into 2 components. i. e. : ux and uy. 2020/10/28 By Mr. NGAN HON SHING ux=u cos ux – a constant horizontal velocity uy – affected by gravitational acceleration (g) 7

Simulation of projectile motion On It moves the other horizontally hand, it also in a moves constant velocity cos ) vertically in vy u where x (i. e. vuy=u y+ gt where uy = u sin 2020/10/28 By Mr. NGAN HON SHING ux 8

Simulation of projectile motion(2) Combine 2 motions. It forms a projectile motion 2020/10/28 By Mr. NGAN HON SHING 9