Kinematics/Free Fall By Dan Gallagher, Stephanie Johnson, Kim Grauf, and Ryan Morton

Some Key Terms Speed –Measures how fast something is moving Velocity –Speed in a certain direction Instantaneous Average Acceleration –Change of velocity in a given time

Free Fall A state of falling without air resistance (only force is gravity) Acceleration is –9.8 m/s 2 Use three of the following equations

Kinematics v=d/t a= (vf-vi)/t d= ½ at 2 + v i t 2ad=vf 2 -vi 2

A ball is dropped from 7 m above the ground. How fast is it moving 1.2 seconds later? Kinematics Examples A rock is dropped from a cliff that is 50 m high. If you throw a ball down from the cliff 2 seconds later so that is reaches the ground at the same time as the rock, how fast must the ball be thrown? m/s m/s

More Kinematics Examples a) How long does it take to reach its maximum height? seconds b) How fast and in what direction is the bullet moving after 3 seconds? Up at m/s A bullet is fired straight up into the air with an initial speed of 440 m/s.

The Quiz! 1.) A race car can slow down with an acceleration of –11 m/s 2. If the car is going 55 m/s, how many meters will it take to stop? d= meters Givens: a = -11 m/s 2 v i = 55 m/s v f = 0 m/s d = ? Equation—2ad=v f 2 -v i 2

The Quiz Continues Givens: a = -9.8 m/s 2 t = 8 seconds v f = ? v i = 0 m/s 2.) A stone falls freely form rest for 8.0 seconds. A) What is the final velocity? Equation—a=(v f -v i )/t v f =-78.4 m/s

#2 continued… B) What distance does the stone fall during this time? Equation—d=1/2at 2 +v i t Givens: d = ? a = -9.8 m/s 2 t = 8.0 seconds v i = 0 m/s d = meters

There’s More?! 3.) You are driving down a street in a car at 55 km/hr. Suddenly a child runs into the street. If it takes you 0.75 seconds to react and apply the brakes, how many meters will you have moved before you begin to slow down? Givens: v f = 96 m/s t = 8 seconds a = ? v i = 32 m/s Equation—a = (vf-vi/)t a = 8 m/s

Last One! 4.) Determine the final velocity of 22 m/s accelerated uniformly at the rate of 1.6 m/s 2 for 6.8 seconds. Givens: t = 6.8 seconds a = 1.6 m/s 2 v i = 22 m/s v f = ? Equation—a=(v f -v i )/t v f = m/s

Extra Tips for Final Go over your picket fence/Galileo lab Go over chapter 2, pgs Worksheet worksheets on Kinematics Kinematics take home quiz

The End!