1. Free Fall and Terminal Velocity CH4 Physics A Winter, 2010-2011

2. Acceleration of Gravity, Free Fall, and Projectile Motion

3. Acceleration of Gravity The acceleration of gravity near the earth’s surface is 9.8 m/s 2 for ALL objects. This means that objects will accelerate at a rate of 9.8 m/s every second when in free fall. Equation – V = g x t Galileo dropped a cannon ball and musket shell and found they landed at the same time

4. Example Problem Example Problem: If an object is dropped from a building, how fast will it be going if it falls for 4 seconds? V = g x t V = (9.8 m/s 2 ) x (4 seconds) = 39.2 m/s (which is about 100 mph)

5. Example #2 You want to know how high above the ground you are, so you drop a rock off a tall bridge. Distance = ½gt 2 You count and see it takes 7.3 seconds to hit the river.

6. Example #2 You want to know how high above the ground you are, so you drop a rock off a tall bridge. Distance = ½gt 2 You count and see it takes 7.3 seconds to hit the river. Thus d = ½ * (9.8 m/sec 2 ) * (7.3sec) 2 D = 267 meters or 876 feet tall

7. Free Fall – When something falls through the air it is experiencing free fall (meaning it accelerates at a rate of 9.8m/s 2 ). Terminal Velocity – The velocity reached when the force of friction (air resistance) becomes equal to the force of gravity pulling down. – Diagram The force of air resistance going up equals the force of gravity going down F air F gravity 102,000 feet 614 mph Terminal velocity helps flying squirrels jump from tree to tree

8. Terminal Velocity Two primary factors affect Terminal Velocity. Area (how much air is caught under it) Mass (how much air can be pushed out of the way). Heavier objects increase TV while wider objects decrease it.

9. Terminal Velocities Compared 134 mph 20 mph 200 mph 204 mph74 mph 20 mph 2 mph