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Vectors and Projectile Motion. Vectors and Scalars. Scalar: any type of quantity that only has an amount (magnitude) Ex. mass, volume, time, speed. Vectors and Scalars. Vector: any type of quantity that has both an amount (magnitude) and direction Ex. Velocity and Acceleration. Vectors.
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Vectors and Scalars • Scalar: any type of quantity that only has an amount (magnitude) • Ex. mass, volume, time, speed
Vectors and Scalars • Vector: any type of quantity that has both an amount (magnitude) and direction • Ex. Velocity and Acceleration
Vectors • Any type of vector is represented by an arrow • The size of the arrow indicates the magnitude, and the way it is pointing indicates the direction
Velocity Vectors Ex. 20 m/s east 30 m/s east
Adding vectors • When two vectors act in the same direction on an object, they are added together • When two vectors act in opposite directions on an object, they are subtracted • When two or more vectors are combined, the final vector is called a resultant
Adding vectors at angles • Suppose two vectors act on the same object at right angles to each other. How is the resultant obtained?
Adding vectors at angles • Ex. A plane is flying at 80 km/hr to the north, and a wind is blowing 60 km/hr to the east. What is the planes resultant speed?
Adding vectors at angles First, draw the two vectors head to tail. 60 km/hr east 80 km/hr north
Adding vectors at angles Draw in the resultant: 60 km/hr east 80 km/hr north
Adding vectors at angles Use the Pythagorean theorem to determine the size of the resultant: Resultant: 100 km/hr 80 km/hr north 60 km/hr east
Components of vectors • Two vectors can be combined into one to find a resultant; the opposite can also be done, one vector can be split into two • These are known as component vectors; they make a right angle with each other
Components of vectors Ex. A ball has a velocity of 20 km/hr northwest; what are the horizontal (west) and vertical (north) components of this velocity?
Components of vectors First, draw out the original vector: 20km/hr northwest
Components of vectors Next, draw out the two components: North component 20km/hr northwest West component
Components of Vectors • How do you tell how big each component is? • Measure with a ruler (when drawn to scale) or use trig functions (sin, cos, tan) • A ruler will be easier, but trig functions will be more accurate
Projectile Motion • Projectile motion: motion of objects (projectiles) as they move through the air (both horizontally and vertically) under the influence of gravity
Projectile Motion • Horizontal motion of a projectile: • When friction is ignored, a projectile moves horizontally with constant velocity
Projectile Motion • Vertical motion of a projectile: • When friction is ignored, a projectile moves vertically with constant acceleration
Projectile Motion • When these two vectors are put together, they form the path of a projectile, which is parabolic in shape. Constant velocity Constant acceleration
Projectiles launched at an angle • When an object is launched at an angle, it also follows a parabolic path (if air friction is ignored) • The distance that the projectile follows is determined by the angle at which it was launched • Horizontal velocity: stays the same • Vertical velocity: goes to zero, then increases
Satellite motion • When an object moves fast enough horizontally so that its path matches the curve of the Earth, the object is said to be in orbit
Keplers Laws of Planetary Motion • Johannes Kepler: 1571-1630 • Formulated three laws of planetary motion
Keplers Laws of Planetary Motion • Based his ideas on data obtained from Tycho Brahe (Court Astronomer for King Frederick II of Denmark) • 20 years worth of data
Keplers 1st law of planetary motion • The paths of all of the planets are ellipses, not circles, with sun at one focus of the ellipse
Keplers 1st law of planetary motion • Most planetary orbits are fairly circular; if they are not perfectly circular, the orbit has a certain amount of eccentricity (off center) • Most eccentric orbits: Mars and Pluto
Keplers 2nd law of planetary motion • An imaginary line from the sun to a planet (or from a planet to a moon) sweeps out equal areas in equal times.
Keplers 2nd law of planetary motion • What equal areas in equal times means for planet movements: • When you are closer to the sun, you go faster • When you are farther from the sun, you go slower