Projectile Motion CH 5 What is a vector

Projectile Motion CH. 5

What is a vector? • A quantity with both magnitude and direction is known as a vector quantity. • A quantity with magnitude only is known as a scalar quantity.

• A resultant is the sum of two or more vectors. • Vectors in the same direction add while those in opposite directions subtract.

What about right angles? • The Pythagorean Theorem is used if the vectors are at right angles to each other.

A vector can be resolved into two vectors at right angles to each other. This pair of vectors are called components (parts) of the vectors they replace.

What is a projectile? • An object cast above the earth undergoes both vertical and horizontal motions and is called a projectile. • Ex. A cannonball, missile, kicked football, longjumper, skier(picture at right), etc.

What is a projectile?

What isn’t a projectile?

Are horizontal and vertical motions related? • The horizontal and vertical motions of a projectile are totally independent of one another. • A projectile begins to lose vertical speed the instant it leaves the launcher (at a rate of 10 m/s 2).

What is trajectory? • A projectiles trajectory refers to the path that it follows as it travels through the air. • The trajectory traces out a parabolic path as it ascends, reaches its peak and then descends.

What angle is best? • A projectile will have maximum horizontal distance if it is fired at an angle of 45 degrees. • This maximizes both horizontal and vertical components. • In air, the angle is slightly less due to wind resistance.

Which angle is best for distance?

What is orbit? • If a projectile is fired at a great enough velocity, the curve that it traces out will match the curve of the earth. • When this happens the object will be in orbit. An example is the space shuttle.

When is a projectile a satellite? • This only occurs when the object is above the drag of the atmosphere. Such an object in orbit is known as a satellite.

Meteorites • An object that falls into our atmosphere from outer space is moving so fast that it almost always burns up before it hits the ground.

Is the moon a satellite? • Satellites can fall around the earth for many years before their orbits decay and they fall back to earth. • The moon is a projectile that we call a natural satellite.