1. Friction in Motion
Gravity and Motion

2. 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

3. 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

4. All Objects Fall with the Same Acceleration

5. 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

6. 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

7. 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.

8. 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)