 ## Presentation on theme: "Projectile Motion https://sites.google.com/site/winfailphysics /all-videos/extreme-grocery-shopping https://sites.google.com/site/winfailphysics /all-videos/extreme-grocery-shopping."— Presentation transcript:

What is a projectile? A projectile is something that is in free fall (so the only force acting on it is gravity) and as it falls it follows a parabolic path. A thrown baseball, an arrow shot from a bow, a rock kicked off a bridge – all of these are examples of projectiles

Which hits the ground first? Which hits the ground first, the dropped ball or the fired one? It would seem as if the ball fired from the gun is going so much faster than the dropped ball and it would take longer to hit the ground……..But they both hit at the same time.

How can this be????? There are types of motion happening at the same time and they have NO EFFECT upon each other at all – ever! There are 2 DIFFERENT types of motion happening at the same time and they have NO EFFECT upon each other at all – ever! Vectors help us analyze the separate motions

The projectile moves horizontally (in the x direction) at Constant Velocity These are x component vectors – Note how each is the SAME length. That is because motion in the x direction is constant

The projectile moves vertically with ACCELERTAION (because gravity is pulling it down) at the same time as it is moving horizontally These are the y components. Note how they get progressivley longer as the projectile continues in its path. That is because gravity is pulling downward, the object is accelerated and thus is falling faster and faster each second

Put them together and you have projectile motion. The vector sum of the x and y components is called the resultant and traces the actual path of the object.

Because the two different motions are separate, you MUST use different formulae to describe or solve for them For the y direction Velocity changes (because of the acceleration due to gravity) so use : d = ½ gt 2 or a = Δ v Δ t For the x direction: Velocity is constant so use: V = Δ d Δ t

To solve for how far (distance) in the y direction: If a pumpkin is launched from a catapult and it takes 6 seconds to hit the ground, what is its max height? KNOW : Time up = time down Total time = 6 s so ½ time = 3 sec FIND : Dist in the y d = ½ gt 2 = ½ (10 m/s 2 ) 3 s 2 = 5 (9) = 45 m

To solve for time in the y direction: If a snow cone is dropped from the top of the 25 meter tall bleachers, how long does it take to hit the ground? KNOW : d = 25 m FIND : time in the y d = ½ gt 2 25m = ½ (10 m/s 2 ) t 2 25m = (5) t 2 5 = t 2 2.2 s = t

To solve for distance in the x direction (constant velocity) If a If a

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