Gravity and Acceleration
And You
Gravity What is Gravity? –1. Gravity = force of attraction between 2 objects as a result of their masses. On Earth the force between an object on Earth, and the Earth results in what we consider a constant acceleration… This is because the Earth is so massive in comparison to objects on earth.
Aristotle and the bunch For many years most people believed Aristotle’s belief that heavier objects fall at a faster rate than lighter objects. Makes sense, right?
Groovy Galileo Galileo disputed Aristotle and suggesting that objects on Earth fall at the same rate. No matter their weight. Through scientific tests he was able to show his theory was Supported by his results!!! HEAVIER objects DO NOT fall faster than a LIGHTER objects.
Acceleration due to Gravity When air resistance doesn’t influence objects on Earth, they accelerate at 9.8 m/s/s or 9.8 m/s 2. Acceleration from Gravity = g (always lower case) Note: g is NOT gravity, just the acceleration due to gravity on earth.
?? 9.8 m/s/s ?? If an object is dropped with no initial velocity then after 1 second it is traveling at a rate of 9.8 m/s (*note it did not travel 9.8 m!!!) After 2 seconds it is traveling at a rate of = 19.6 m/s After 3 seconds? = 29.4 m/s It did not travel 29.4 m, it has a speed of 29.4 m/s!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
What can I do with this? v i = initial velocityv f = final velocity a = acceleration g = acceleration due to gravity t = timed = distance Calculate final velocity of a falling object. V f = at + v i or v f = gt + v i Calculate the distance traveled by a falling object. d = 1/2at 2 or d = 1/2gt 2
How fast is it falling
How far has it fallen?
Practice Problems How far does a ball fall after 2.7 seconds? Position (y) = ½ * g * t 2 (y) = ½ * 9.8(m/s 2 ) * = 4.9m/s 2 * 7.29s 2 = m = 36 m
How about some more sweet equations If I throw an object up, how high will it go? y top = v i 2 / 2g How long with the ball stay in the air? t = 2y top / g Where does that come from?
A stone is thrown into the air with an initial velocity of 9.8 m/s. How high will it go? Y top = V i 2 / 2g
How long with the ball stay in the air from the Y (top) down? (4.9m high) t = 2y top / g
Therefore: The total time this object stays in the air from the time of release to the time it returns to the point of release is: 2s Time up = time down