Transcript Falling objects

FALLING OBJECTS
BELLRINGER
 If Wile E. Coyote and a boulder fall off a cliff at
the same time, which do you think will hit the
ground first?
OBJECTIVE
 Explain the effect of gravity and air resistance on
falling objects
 Explain why objects in orbit are in free fall and
appear to be weightless
 Describe how projectile motion is affected by
gravity
MISCONCEPTIONS
 Heavier objects will fall faster than lighter
objects
 Objects fall at a constant speed
 All objects have the same force of gravity
http://www.youtube.com/watch?v=_mCC-68LyZM
ACCELERATION OF GRAVITY
 Galileo Galilei dropped items with
different masses off the Leaning
Tower of Pisa in Italy to prove that
ALL OBJECTS FALL AT THE SAME
RATE
 This happens because the
acceleration of gravity – 9.8 m/s2 – is
the same for all objects
VELOCITY OF FALLING OBJECTS
 A falling object accelerates at a
constant rate
 The object falls faster and farther each
second than it did the second before
 You can calculate the change in velocity
(Δv) of a falling object by using the
following equation:
 Δv = g × t
AIR RESISTANCE
 Air resistance is the force that
opposes the motion of objects through
air
 The amount of air resistance acting on
an object depends on the size, shape,
and speed of the object
 Notice mass is NOT a factor
 Objects with similar size, shape and
speed but with different masses will fall
at the same rate
TERMINAL VELOCITY
 As the speed of a falling object
increases, air resistance increases
 Eventually the upward force of air
resistance continues is equal to the
downward force of gravity
 The object then falls at a constant
velocity called the terminal
velocity
FREE FALL
 When the only force acting on an
object is gravity, the object is in free
fall
 Because air resistance is a force, free
fall can occur only where there is no air
 Space
 http://www.youtube.com/watch?v=KDp1tiUsZw8
 Vacuum
 http://www.youtube.com/watch?v=_XJcZ-KoL9o
ORBITING
 An object is orbiting when
it is traveling around
another object in space
 When a spacecraft orbits
Earth, it is moving forward
 But the spacecraft is also in
free fall toward Earth
 The combination of these
two motions causes orbiting
CENTRIPETAL FORCE
 The unbalanced force that causes
objects to move in a circular path
is called a centripetal force
 Gravity provides the centripetal
force that keeps objects in orbit
PROJECTILE MOTION
 Projectile motion is the curved path
an object follows when it is thrown or
propelled near the surface of the Earth
 Examples:
 a frog leaping
 water sprayed by a sprinkler
 a swimmer diving into water
 balls being juggled
 an arrow shot by an archer
HORIZONTAL VS.VERTICAL MOTION
 Two motions combine to form the curved
path:
 Horizontal Motion – a motion that is parallel
to the ground
 The applied force (push or a pull) is usually the
horizontal force
 Vertical Motion – motion that is perpendicular
to the ground
 Gravity is usually the vertical force and it pulls the
object down at an acceleration of 9.8 m/s2
 This rate is the same for all falling objects