1. Falling objects

2. 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?

3. 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

4. misconceptions Heavier objects will fall faster than lighter objects
Objects fall at a constant speed
All objects have the same force of gravity

5. 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

6. 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

7. 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

8. 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

9. 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
Vacuum

10. 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

11. 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

12. 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

13. 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