Free Fall

Vertical motion of an object moving with a constant acceleration. Vertical motion of an object moving with a constant acceleration. The constant acceleration is caused by gravity alone. The constant acceleration is caused by gravity alone. In the absence of air resistance, all objects in free fall have the same constant acceleration. In the absence of air resistance, all objects in free fall have the same constant acceleration. On Earth, the free fall acceleration = g On Earth, the free fall acceleration = g = 9.80 m/s 2 downward = 9.80 m/s 2 downward

Free Fall Objects in free fall have the same acceleration regardless of the direction of their motion. Objects in free fall have the same acceleration regardless of the direction of their motion. regardless of the direction of their motion regardless of the direction of their motion The 4 equations for motion with constant acceleration are used to solve free fall problems. The 4 equations for motion with constant acceleration are used to solve free fall problems. The acceleration is known to be 9.80 m/s 2 downward The acceleration is known to be 9.80 m/s 2 downward Either up or down can be designated as the positive direction. However, once a designation is made, stick with it throughout the problem! Either up or down can be designated as the positive direction. However, once a designation is made, stick with it throughout the problem! Pay careful attention to signs when solving problems. Careless use of signs will result in errors. Pay careful attention to signs when solving problems. Careless use of signs will result in errors.

Ex. 1: On the Stuntman’s Free Fall ride at Six Flags, the cage begins its fall from rest. It falls freely for 1.70 s. What is the distance through which it falls freely? Given: v i = 0 a = 9.80 m/s 2 a = 9.80 m/s 2  t = 1.70 s  t = 1.70 s Find:  d = ?  d = v i t + ½ a  t 2 = 0+½ (9.80 m/s 2 )(1.70 s) 2 = 14.2 m

Ex 2: How fast is the cage on Free Fall moving at the end of its free fall? Given: v i = 0 a = 9.80 m/s 2 a = 9.80 m/s 2  t = 1.70 s  t = 1.70 s Find: v f = ? v f = v i + a  t = 0 + (9.80 m/s 2 )(1.70 s) = 0 + (9.80 m/s 2 )(1.70 s) = 16.7 m/s = 16.7 m/s

Ex 3: An arrow is shot straight up into the air. It takes 5.0 s to reach its highest point. What was its speed as it left the bow? Given:  t = 5.0 s a = m/s 2 a = m/s 2 v f = 0 v f = 0 Find: v i = ? v f = v i + a  t v f = v i + a  t v f – (a  t )= v i 0 - (-9.80 m/s 2 ) (5.0 s) = v i = 49 m/s = 49 m/s