Transcript Gravity & Motion

Friction in Motion
Gravity and Motion
Terms
• Terminal velocity~ the constant
velocity of a falling object when the
size of the upward force of air
resistance matches the size of the
downward force of gravity
• Free fall~ the condition and object is in
when gravity is the only force acting on
it
• Projectile motion~ the curved path an
object follows when thrown or
propelled near the surface of the Earth
All Objects Fall with the
Same Acceleration
• Acceleration due to gravity
– Fall at same rate because acceleration due
to gravity is the same for all objects
– Force of gravity larger between Earth and
a larger object than Earth and a small
object
– Difference in force canceled by difference
in mass
• Accelerating at a constant rate
– Objects accelerate toward Earth at a rate
of 9.8 m/s2
All Objects Fall with the
Same Acceleration
Air Resistance Slows Down
Acceleration
• Air Resistance affects some objects
more than others
– Depends on size and shape of object
• Acceleration stops at the terminal
velocity
– Upward force from air resistance continues
to increase until it exactly matches the
downward force of gravity
– Object falls at constant velocity
• Free fall occurs when there is no air
resistance
Orbiting Objects Are in
Free Fall
• Two motion combine to cause orbiting
– Forward motion & free fall
– Figure 7 page 142 (may want to sketch)
• The role of gravity in orbiting
– Centripetal force is the unbalanced force
which causes objects to move in a circular
pattern
– Gravity provides centripetal force
Projectile Motion and Gravity
• Horizontal Motion
– Object moves parallel to the floor
After the ball leaves the pitcher’s hand,
its horizontal velocity is constant.
The ball’s vertical
velocity increases
because gravity
causes it to
accelerate
downward.
The two motions
combine to form
a curved path.
Projectile Motion and Gravity
• Vertical Motion
– Gravity pulls object making object move
perpendicular to the floor
– Figure 10 page 144 (may want to sketch
tonight)