Free Fall: How Fast and How Far Chapter 2.5 & 2.6

Free Fall Objects only influenced by gravity Assume no air resistance Acceleration due to gravity= ~10m/s2 Actual value= 9.81 m/s2

How Fast: Elapsed time: time since the beginning of the fall Acceleration= change in speed/elapsed time Therefore, v=gt. (velocity=acceleration due to gravity/elapsed time)

Practice Problems: Let’s say you drop a ball, how fast will it be traveling at 1 second? 10m/s2= speed/1s speed= 10m/s How fast will the ball be traveling at 2 seconds? 10m/s2= speed/2s Speed= 20 m/s

So far, we have only talked about examples where an object is moving straight down. When an object is thrown upward, it eventually reaches the point where it must come down.

Upward motion maximum point downward, ball slows by 10m/s each second from its initial upward velocity to zero velocity. maximum point the ball has a speed of 0 m/s. downward, acts as free falling object that was dropped from rest increasing its speed by 10 m/s each second.

Practice Problem: A person throws a baseball straight up into the air with an initially velocity of 40 m/s second. How long before the ball has a velocity of 0 m/s? 4 seconds How fast will the ball be traveling at 7 seconds if there is nothing for it to run into? 30 m/s downward

How Far Question: How far does an object fall in 1 s? Answer: NOT 10 m How fast was an instantaneous speed not an average speed, the speed of an object does not maintain a speed of 10 m/s throughout the second of fall. Average speed= (final velocity-initial velocity) 2

Answer: Average velocity= distance/ time (10-0)/2 = distance/ 1 s Distance= 5 m

Practice Problem: How far does an object fall after 2 seconds? Instantaneous speed at 2 seconds= 20 m/s Average speed= (20-0)/2= 10 m/s 10 m/s= distance/ 2 s Distance= 20 m

How Far: The distance an object travels during free fall is: d= ½at2 Practice Problem: How far does an object fall after 3 seconds? distance= ½*10*32 =45 m