Chapter 3 Section 3 Mrs. Faria Free Fall Chapter 3 Section 3 Mrs. Faria

Galileo’s Experiment Galileo dropped several objects with different weight and from different heights He concluded that when air resistance is neglected, all objects in free fall had the same acceleration

Acceleration Due to Gravity The acceleration of an object in free fall that results from the influence of Earth’s gravity. Gravity = 9.8 m/s2 Comes from the center of the Earth Differs from planet to planet

Acceleration Due to Gravity

Acceleration Due to Gravity g = -9.8 m/s2 Max Height Velocity is ZERO Acceleration = -9.8 m/s2 Way Up Velocity is decreasing Speed is decreasing SLOWER Acceleration = -9.8 m/s2 Way Down Velocity is decreasing Speed is increasing FASTER Acceleration = -9.8 m/s2

Maximum Height What is the velocity of the ball at the top of its flight? 0 m/s What is the acceleration of the ball at the top of its flight? -9.8 m/s2 What would happen if the both velocity and acceleration are zero at the top of the ball’s flight? The ball would float.

Acceleration Due to Gravity g = -9.8 m/s2 Velocity (m/s) Way Down Velocity is decreasing Speed is increasing FASTER Acceleration = -9.8 m/s2 DROP When an object is dropped, the initial velocity is zero.

Kinematics Equations ∆x becomes ∆y a becomes g vf = vi + at Kinematics in the X Kinematics in the Y (FREE FALL) vf = vi + at vfy = viy + gt ∆x = vit + ½ at2 ∆y = viyt + ½ gt2 vf2 = vi2 + 2a∆x vfy2 = viy2 + 2g∆y

Problem Solving (Points to Remember) Acceleration is always -9.8 m/s2 At maximum height Velocity is zero Acceleration is -9.8 m/s2 Always let your starting position be zero (up=+ & down = -) When an object is dropped, initial velocity is zero When an object is thrown into the air, it must have an initial velocity Time up is equal to time down At any given point, velocity up is equal to velocity down. If the object lands below the starting position, then ∆y is negative. Velocity going up is always positive, velocity going down is always negative.