Presentation on theme: "Free Fall Acceleration"— Presentation transcript:
1Free Fall Acceleration Falling ObjectsFree Fall Acceleration
2Freely falling bodies undergo constant acceleration If air resistance is disregarded, all objects dropped near the surface of a planet fall with the same constant acceleration.This acceleration is due to gravitational force and is known as free fall.On Earth, ag has a magnitude of m/s2 or -32 ft/s2. (It is negative because it directed downward toward earth.)pg56 Physics Serway /Faugh (Holt)
3GRAVITY IS NOT EXACTLY THE SAME AT ALL EARTH LOCATIONS This visualization of a gravity model was created with data from NASA's Gravity Recovery and Climate Experiment (GRACE) and shows variations in Earth’s gravity field.Gravity is determined by mass. Earth’s mass is not distributed equally, and it also changes over time.The colors in this image represent the gravity anomalies measured by GRACE. One can define standard gravity as the value of gravity for a perfectly smooth 'idealized' Earth, and the gravity 'anomaly' is a measure of how actual gravity deviates from this standard. Red shows the areas where gravity is stronger than the smooth, standard value, and blue reveals areas where gravity is weaker.Weak Strong
4Different Planets = Different free fall rates of acceleration
50n August 2, 1971, a demonstration was conducted on the moon by astronaut David Scott. He simultaneously released a hammer and a feather from the same height above the moon’s surface. They both fell straight down and landed on the lunar surface at exactly the same moment. (ag on the moon = m/s2 compared to Earth’s -9.81m/s2pg56 Physics Serway /Faugh (Holt)
6pg56 Physics Serway /Faugh (Holt) When there is no air resistance, all objects fall with the same acceleration regardless of their masses.The feather and the apple are released in a vacuum chamber. The two objects fell at exactly the same rate, as indicated by the horizontal alignment of the multiple images.The pictures shows that even though the amount of time between pictures isequal, the displacement in each timeinterval did not.Both the apple and the feather werein free fall and accelerated to Earthat the rate of 9.81m/s every second(-9.81m/s2).
8Distance Fallen = ½gt2Notice the relationship between time, g and distance fallen. Distance increases proportionally with the square of the time
9The acceleration never changes throughout the ball’s travel (although Objects thrown into the air have a downward acceleration as soon as they are released.A soon as the ball is released, with an upward velocity of 10.5 m/s, it has ag = m/s2.After 1s, the ball’s v is 0.69 m/s but ag is still m/s2 (still moving upward at this point) .After 2s, the ball’s v is 9.12 m/s and ag is still m/s2 (moving downward) .The acceleration never changesthroughout the ball’s travel (althoughthe sign changes with direction).
10Graph showing the velocity of the ball plotted against time.
12WeightlessnessAstronauts on the International Space Station are weightless because when they are in Earth orbit they are in a continual state of free fall. Because they are traveling at such a high velocity, the Earth curves away beneath them.
14Weightless in a special aircraft known as the “vomit comet” that flies a parabolic path for a very short period of weightlessness.
15Free-fall and Terminal Velocity If the Earth had no atmosphere, when skydivers accelerate in free-fall, they would continue to accelerate to the ground, even if they could open their chutes (which would be difficult without an atmosphere).
17Terminal velocity depends on an object’s mass, shape, and size. A skydiver spread out typically has a terminal velocity of about 55 m/s (123 mph).If the sky diver curls into a ball, terminal velocity may be close to 90 m/s (200 mph).
18When the chute opens, and air resistance increases, the skydiver decelerates to a new slower terminal velocity – typically about 5m/s (11mph).
19Felix Baumgarter – Highest (24 mi. ) and Fastest Free Fall (1357 Felix Baumgarter – Highest (24 mi.) and Fastest Free Fall ( km/h (843.6 mph), or Mach 1.25)