# Vectors & Projectile Motion Physics LG Jan. 30, 2009.

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Vectors & Projectile Motion Physics LG Jan. 30, 2009

Motion is Relative ► Frame of Reference - perspective from which you observe

Truck at Rest If the ball is thrown at 60 km/h relative to the truck, at what velocity will the person catch the ball at?

Truck Moving Away ► ► If the ball is thrown at 60 km/h west relative to the truck and the truck moves at 40 km/h east relative to the catcher, at what velocity will the person catch the ball at?

Truck Moves Towards ► ► If the ball is thrown at 60 km/h west relative to the truck and the truck moves at 40 km/h west relative to the catcher, at what velocity will the person catch the ball at?

► Scalar - measurement of magnitude only  Ex) mass, volume, speed ► Vector - measurements with both magnitude and direction  Ex) velocity, acceleration, force

arrowhead = direction length of arrow = magnitude Vectors

Resultant – sum of vectors

► Boat crossing river animation… http://www.schulphysik.de/suren/Applets.htm l http://www.schulphysik.de/suren/Applets.htm l

Pythagorean Theorem a 2 + b 2 = c 2 a 2 + b 2 = c 2

► c 2 = a 2 + b 2 ► c 2 = 80 2 + 60 2 ► c 2 = 6400 + 3600 ► √c 2 = √10,000 ► c = 100 km/hr

Example Problem ► c 2 = a 2 + b 2 ► c 2 = 4 2 + 3 2 ► c 2 = 16 + 9 ► c 2 = 25 ► c = 5 km/h

Vector addition ► Pythagorean Theorem - ► Parallelograms - ► Head-to-tail method - ► Trigonometry -

What is the vertical and horizontal component of a vector? http://www.batesville.k12.in.us/Physics/APPhyNet/Vectors/Hor_&_Vert_Comps.html

Projectile Motion Projectile – an object moving through air affected by gravity Projectile – an object moving through air affected by gravity

Projectile Demos ► Shooter/ Dropper ► Monkey and Hunter

Projectile Motion Horizontal and vertical motion act independently Horizontal and vertical motion act independently

How fast is the ball thrown?

► Vertical ► d=.5at 2 ► 5 =.5(10)t 2 ► t= 1 second ► Horizontal ► v= d/t ► v= 20m/1s ► v= 20 m/s The ball is thrown at 20 m/s!

What angle should a ball be kicked to get the farthest? Upwardly-Moving Projectiles

Projectiles launched at the same speed but different angles.

Shot Put - 45º is not the ideal angle, why? You are already off the ground 1-2 meters.

45º is the ideal angle for high speed projectiles either. Why? 45º is the ideal angle for high speed projectiles either. Why? Air resistance must be considered.

Fast Moving Projectiles ► What would happen if you threw a ball so fast that the curvature of the earth came into play?

Fast Moving Projectiles ► Satellite- a projectile traveling fast enough to fall around the earth rather than into ► To stay in orbit around the earth, a satellite needs to travel at 8 km/s!

Hang Time

Due Next Week   POTW   11s Bull’s eye lab   12s Rocket Lab   30s Motion Worksheet #1   31s Motion Worksheet #2   32s Motion Review   Test will be next Thursday Feb 5 th ► ► Study the 1s, 2s, labs, and worksheets ► ► Use the back page of booklet under motion for note sheet for test.