Acceleration Due to Gravity Free fall - falling under influence of gravity w/o ______ ____________ Distance proportional to time squared Speed changes linearly with time The ____________________________ is the same for all objects and is often represented by the letter ____ g = 9.8 m/s2 toward the Earth. air resistance acceleration due to gravity g

Falling objects zero 9.8 m/s2 symmetry The velocity at the top of the path is _______ The acceleration of the object throughout the motion is always ____________ Trajectories show up and down ____________ zero 9.8 m/s2 symmetry

Falling objects For a falling body, a = g = 9.8 m/s2 down

Falling objects Notice that the distance the object falls during each second is larger than the distance that it fell in the previous second… WHY?

Acceleration Due to Gravity d = ½ at2 vf = vi + at a = g = 9.8 m/s2 down or -9.8 m/s2 Remember that if up is labeled as the ________________, down must be labeled as the ________________ The velocity at the top of an object’s path is _____ when it is in __________. positive direction negative direction zero freefall

An object is dropped from the top of the Willis Tower, which is 443 meters tall. How long will it take the object to reach the ground? How fast is the object travelling when it lands on the ground? d = ½ a t2 d = - 443 m a = - 9.8 m/s2 - 443 m = ½ (-9.8 m/s2) t2 t = ? - 443 m = (-4.9 m/s2) t2 t = 9.51 s vf = vi + a t d = - 443 m vf = 0 m/s + (-9.8 m/s2)(9.51 s) a = - 9.8 m/s2 vf = - 93.2 m/s t = 9.51 s Why is the answer negative? vf = ? Because the object is moving down! vi = 0 m/s