Park Physics with Sean Lally - 2017-2018

1.  Find the acceleration of a car that goes from rest to 30 m/s in 6 seconds.  Also find how far it travels in this time. 2.  A ball is dropped on Mercury where the surface gravity is 3.7 m/s/s.  If it is released from 10-m above the surface, how long will it take to fall and how fast will it be traveling before it hits. 3.  A soccer ball is kicked off a 25-m tall cliff horizontally at 10 m/s.  How long will it take to hit the ground and how far from the base of the cliff (horizontally) will it land?

Here are some practice problems related to the equations of motion: 1.  A car starts from rest and accelerates at 5 m/s/s.  After 8 seconds of continual acceleration: a.  how fast is it moving? b.  how far has it gone? (40 m/s, 160 m) 2.  If you were to drop a ball (from rest) from a 50-m tall tower, find: a.  how long it takes to hit the ground? b.  how fast it will be traveling right before it hits? (3.19 seconds, 31.3 m/s) 3.  Think about question number 2 again.  This time, the ball is kicked horizontally from a 50-m tall tower at 20 m/s. a.  how long will it take to hit the ground? b.  how far (horizontally) will the ball travel c.  What effect does the horizontal speed (20 m/s) have on this problem? (3.19 s, 64 m) Other things to review: - Difference between velocity (or speed) and acceleration - The correct units for velocity, distance, and acceleration - The correct symbols for velocity, distance, and acceleration - Graphs of motion and how to i

Good work today, everyone!  No homework, unless you're still confused by all of this - in which case, review the problems that led up to today.  Specifically, the zip line problems - the answers are all around 1 second for time (t) and 9 m for horizontal distance (d). Thanks for today, folks.  Video people, feel free to email me the best videos you got.

Small person (46 kg -- about 101 lb) Drop height (d) = 5.7 m above pool Horizontal speed (v) = 8.4 m/s Medium person (63 kg -- about 139 lb) Drop height (d) = 5.4 m above pool Horizontal speed (v) = 8.8 m/s Larger person (82 kg -- about 181 lb) Drop height (d) = 4.8 m above pool Horizontal speed (v) = 9 m/s Choose the person size that is closest to your own.  Using the vertical distance above ground (d) and horizontal speed (v), calculate the following: time in air horizontal distance traveled We will use the horizontal distance traveled to predict where we should place the hula hoop on Monday.  That will be our target.  Using the zip line will be optional - in fact, we will probably not have enough time for everyone to run. > I have also given you information about how to import movies into Logger Pro.  Try to analyze your own video from class today.  If you get a graph, take a screen shot and bring it to class.

It is due at the BEGINNING of class tomorrow. Forget not, physics phriends.

Review the recent homework AND the mini-lab from today's class. Then try this problem. A soccer ball is kicked from a rooftop horizontally at 12 m/s.  If the rooftop is 15-m above the ground, find the following: a.  how long the ball takes to hit the ground b.  how far from the building the ball will land c.  how much longer the ball would be in air if it were kicked twice as hard

This homework is related to the discussion we had in class about horizontal motion vs. vertical motion. A baseball is thrown horizontally at 30 m/s (which is a pretty typical Park pitcher throwing speed).  It leaves the pitcher's hand 1.5 m above the ground. 1. How long would the ball take to hit the ground, if it does not hit a bat (or anything else) first?  Keep in mind this is just like a dropped object, since there is no horizontal acceleration for the ball (after it leaves the pitcher's hand). 2.  How far will the ball travel horizontally in this time.  Hint:  use v = d/t (since there is no horizontal acceleration). 3.  Is there any time difference between this thrown ball and another ball dropped from the same height (instead of thrown)?  Discuss why. 4.  Challenge question.  If the pitcher were standing on a 0.5 m tall mound,  but otherwise throws as above, how long would the ball take to touch ground and how far would it go horizontally?