1. What Goes Up . . .
Must Come Down!

2. Newton’s Three Laws of Motion
inertia – an object maintains its state of rest or uniform motion unless it is acted upon by a force
unbalanced forces – an object accelerates under the effect of a unbalanced force
action-reaction forces – for every action force there is an equal and opposite reaction force

3. Inertia
The biker will continue on his path until acted upon by another force, in this case gravity, air resistance, the ground, a wall, etc.

4. Unbalanced Forces
The man on the left should accelerate toward the right as the other 8 people pull him (as long as they pull him with more force than he pulls them).

5. Action-Reaction Forces
The blast from the rocket is aimed downward, causing a force in the opposite direction, lifting the rocket from the ground.

6. Gravity gravity – the attraction of Earth to everything on it
gravity does not depend on the air; even in a vacuum an object will fall

7. Galileo and Gravity
in 1588, Galileo discovered that different objects fall at the same speed
he did this by dropping different size cannon balls from the Leaning Tower of Pisa
their size or mass does not impact the speed at which they fall

8. Air Resistance
Air resistance interferes with gravity’s pull, causing some objects to fall more slowly than others.
air resistance – the force of air against any object moving through it.
Objects with a larger surface area experience more air resistance.

9. Parachutes
parachute – a large piece of material that slows things down as they fall from great heights
the first parachute was designed by Leonardo di Vinci some 500 years ago.
French “aeronauts” were the first parachute jumpers.
in 1783, a Frenchman parachuted from a tower
in 1797, a Frenchman parachuted from a hot-air balloon
In 1922, the first pilot parachuted from a damaged plane.

10. Acceleration and Terminal Velocity
All objects fall with the same acceleration, that is 9.8 m/s2
In a vacuum, the farther an object falls, the faster it travels.
However, on Earth, air resistance eventually balances out the affect of gravitational pull, and the object falls at a steady speed.
This constant speed is call terminal velocity.

11. Parachutes in Nature
In nature, many seeds travel like tiny parachutes, as do some animals.