FREEFALL ACCELERATION VERTICAL ONE DIMENSIONAL MOTION Objectives Relate

FREE-FALL ACCELERATION VERTICAL ONE DIMENSIONAL MOTION

Objectives � Relate the motion of a freely falling body to motion with constant acceleration. � Calculate displacement, velocity, and time at various points in the motion of a freely falling object.

Bell-Ringer � � � Free Fall “Bell-Ringer” OK Physics Rock-stars…here we go! You have 3 minutes to complete this activity. Your table is going to get two objects. Throw them gently in the air, being careful of the ceiling and your classmates, and record at least 4 observations that you make about the motion of the object you are tossing up. As soon as you have read this, raise your hand so I know you are ready for your objects. Free-Falling

QOTD A hammer and a feather are dropped from the same height above the Earth’s surface…which hits the ground first and why? A hammer and a feather are dropped from the same height above the moon’s surface…which hits the ground first and why? Hammer and Feather

Free Fall � � � Free fall is the motion of a body when only the force due to gravity is acting on the body. The acceleration on an object in free fall is called the acceleration due to gravity, or freefall acceleration. Free-fall acceleration is denoted with the symbols ag (generally) or g (on Earth’s surface).

Free-Fall Acceleration Tips 1. Free-fall acceleration is the same for all objects, regardless of mass. � We will use the value g = 9. 81 m/s 2. 2. Free-fall acceleration on Earth’s surface is – 9. 81 m/s 2 at all points in the object’s motion. 3. Consider a ball thrown up into the air. � Moving upward: velocity is decreasing, acceleration is – 9. 81 m/s 2 � Top of path: velocity is zero, acceleration is – 9. 81 m/s 2 � Moving downward: velocity is increasing, acceleration is – 9. 81 m/s 2 � Velocity Up = Velocity Down at the same height. � Time Up = Time Down for equal heights.

QUESTION Which of the following statements is true of acceleration? � A. Acceleration always has the same sign as displacement. � B. Acceleration always has the same sign as velocity. � C. The sign of acceleration depends on both the direction of motion and how the velocity is changing. � D. Acceleration always has a positive sign. �

� Which of the following statements is true for a ball thrown vertically upward? � A. The ball has a negative acceleration on the way up and a positive acceleration on the way down. � B. The ball has a positive acceleration on the way up and a negative acceleration on the way down. � C. The ball has zero acceleration on the way up and a positive acceleration on the way down. � D. The ball has a constant acceleration throughout its flight.

Sample Problem 1 Falling Object Jason hits a volleyball so that it moves with an initial velocity of 6. 0 m/s straight upward. If the volleyball starts from 2. 0 m above the floor, how long will it be in the air before it reaches maximum height? How high will it go? What is the velocity when it hits the ground? What is the total time in the air?

Assessment � � � 3 -2 -1…grade yourself on your ability to problem solve at this point. It’s time to “DIVIDE AND CONQUER” free-fall acceleration problems!!! The goal, remember, is to be a 3!!!!

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