ch3_mkmk

=Chapter 3 Review = "Projectiles in Motion"

__**3-1: Vector and Scalar Quantities ** //Pages 28 – 29//__


 * Vector** – something that requires both magnitude and direction for a complete description (examples: distance a rock has fallen, how quickly a car accelerates, how hard an object has been pushed)
 * Scalar** – when something can be described with just magnitude alone (examples: elapsed time, mass, or volume)

Scalars can be added, subtracted, multiplied, and divided

__**3-2: Velocity Vectors** //Pages 29 – 31//__

When vectors are drawn, their length is proportional to the magnitude of the quantity they represent When a group of vectors are being added the resultant can be found by drawing each of the vectors to scale in the correct direction so that one vector stars where the preceding one ends http://www.physicsclassroom.com/mmedia/vectors/ao.cfm

In order to find the resultant, use the Pythagorean Theorem:

For examples on how to solve velocity vector problems, see //Page 31//

__**3-3: Components of Vectors** //Pages 31 – 32//__

Resolution of the vector into components can be found by drawing the vector to scale and at the proper angle, finding a rectangle that will just fit around it, and then measuring the sides of the rectangle
 * Resolution of the vector into components** – any single vector can be broken into two pieces that are at right angles to each other

__**3-4: Projectile Motion ** //Pages 33 – 35//__

The horizontal and vertical motions of a projectile are independent of each other
 * Projectile** – any object that is shot, thrown, dropped, or otherwise winds up moving through air
 * Horizontal** – motion with a constant velocity
 * Vertical** – free fall

http://www.physicsclassroom.com/mmedia/vectors/bds.cfm As you can see above, both balls fall the same vertical distance in the same time.The ball's horizontal component of motion remains constant.

__**3-5: Upwardly Launched Projectiles ** //Pages 35 – 38//__

Anything launched upward at an angle will follow a curved path and return to earth unless moving extremely fast due to gravity The projectile after t seconds would be at a point directly under the line it would follow if gravity was not present The horizontal component will not change as the projectile moves, the vertical component will be the same as for another object thrown straight up An object thrown at 90° will have the same range as if it were thrown at 60° at the same speed. An object thrown at 45° will travel farther than any other angle An object thrown straight up will reach a higher maximum height When //vi// is the initial velocity and //Ө// is the angle above the ground, //d// is equal to the total distance travelled:

** //d = (vi^2sin(2Ө))/g// **

A projectile will rise to its maximum height in the same time it takes to fall from that height to the ground if air resistance is negligible.

__**3-6: Fast-Moving Projectiles (Satellites)** //Page 39//__

A ball will fall a set distance no matter how fast you throw it. If the ball is thrown twice as fast, it will go twice as far. If something is thrown faster than 8 km per second, it will never return to the earth; goes into orbit as a **satellite** High altitude puts the satellite beyond the earth's atmosphere where air resistance is almost totally absent

http://www.physicsclassroom.com/mmedia/vectors/sat.cfm The picture above shows a projectile orbiting earth in an elliptical path due to a launch speed greater than 8 km/s.  Satellites are launched above 150 kilometers to avoid grazing the earth's atmosphere and burning up.

REMEMBER KIDS...SCIENCE IS NOT A JOKE!