Presentation on theme: "Motion in One Dimension Free Falling Objects"— Presentation transcript:
1 Motion in One Dimension Free Falling Objects Chapter 2: Section 3Source:
2 Learning TargetsRelate the motion of a freely falling body to motion with constant accelerationCalculate displacement, velocity, and time at various points in the motion of a freely falling objectCompare the motions of different objects in free fallP2.1D, P2.1g, P2.2C
3 The Big Misconception"Wouldn't an elephant free-fall faster than a mouse?“If we are considering the specific type of falling motion known as free-fall, the objects move under the sole influence of gravityMore massive objects will only fall faster if there is an appreciable amount of air resistance present.However, objects that are truly in free fall do not encounter air resistance.Subsequently, all objects free fall at the same rate of acceleration, regardless of their mass.
4 In the absence of air resistance, all objects dropped near the surface of a planet fall with the same constant accelerationThis is why a feather and an apple fall at the same rate if dropped in a vacuumIn the presence of air resistance,an object will eventually reachterminal velocityAir Resistance
5 What is Free Fall?A free falling object is one that is falling under the sole influence of gravity.Any object that is being acted upon only by the force of gravity is said to be in a state of free fall.
6 Characteristics of Free Fall There are two important characteristics of free falling objects:Free-falling objects do not encounter air resistance.All free-falling objects (on Earth) accelerate downwards at a rate of m/s/s (m/s2)The acceleration due to gravity is denoted with the symbols ag or g (on the surface of the Earth)
7 Reviewing Acceleration Remember that acceleration is the ratio of velocity change to time between any two points in an object's path.To accelerate at 9.8 m/s/s means to change the velocity by 9.8 m/s each second.
8 An Example of Free FallIf the velocity and time for a free-falling object being dropped from a position of rest were tabulated, then one would note the following pattern:Time (s)Velocity (m/s)1-9.82-19.63-29.44-39.25-49.0
9 Graphing Free Fall Position vs. Time Graph The slope of any position vs. time graph is the velocity of the objectA curved line on a position versus time graph signifies accelerated motionThe small initial slope indicates a small initial velocity and the large final slope indicates a large final velocity.The negative slope of the line indicates a negative (i.e., downward) velocity.
10 Graphing Free Fall Velocity vs. Time Graph The slope of any velocity vs. time graph is the acceleration of the objectA diagonal line on a velocity versus time graph signifies accelerated motionConstant negative slope indicates a constant negative acceleration
11 Acceleration is constant during upward and downward motion
12 When we throw an object up in the air, it will continue to move upward for some time, stop momentarily at the peak, and then change direction and begin to fall.Because the object changes direction, it may seem that the velocity and acceleration are both changing.Actually objects thrown into the air have a downward acceleration as soon as they are released
14 Velocity and Acceleration During Free Fall Free falling objects always have the same downward accelerationWhen going up, velocity is positive and acceleration is negative (-9.8 m/s2) - the object is slowing downWhen falling down, velocity is negative and acceleration is negative (-9.8 m/s2) - the object is speeding upRemember that when the signs of velocity and acceleration are the same, an object speeds up. When they are opposite, an object is slowing down
15 Calculating Free Fall Velocity To calculate velocity during free fall, use the velocity with constant acceleration equationsvf2 = vi2 + 2a∆yvf = vi + a∆t*a = -9.8 m/s2You can use any of the kinematic equations to solve free fall problems