Physics 218, Lecture IV1 Physics 218 Lecture 4 Dr. David Toback

Physics 218, Lecture IV2 Notes There is a link to a copy of all the handouts on my web page. There are even some handouts which I didn’t handout, but you should pick up. Please make sure you are checking your neo account and that you are receiving there. Please make sure that you are registered for 218 and not 208 on your Math quizzes!!

Physics 218, Lecture IV3 Today’s Lecture Today we’ll concentrate on problem solving techniques for Chapter 2 Mostly examples –Stopping a speeding car –Catching a speeder –Free fall

Physics 218, Lecture IV4 Solving Problems Read (and Re-Read). What are you looking for? Draw a diagram List givens and wants Plan Use reasonable equations and solve Calculate Check Reasonableness and Units For the HW, plug in the numbers and check the answer in the back of the book/on the web. Another way to do the same problem which gives the same answer?

Physics 218, Lecture IV5 How quickly can you stop a car? You’re driving along a road at some constant speed, V 0, and slam on the breaks and slow down with constant deceleration a. How far do you travel before you come to a stop? When you hit the brakes Where you stop

Physics 218, Lecture IV6 Show Show that

Physics 218, Lecture IV7 Speeder A speeder passes a cop sitting by the side of the road and maintains their constant velocity V. The cop moves from rest with constant acceleration a. How much time does it take to catch the speeder? How far did they travel? What is the final cop speed? X Speeder Cop

Physics 218, Lecture IV8 Free Fall Free fall is a good example for one dimensional problems Gravity Things accelerate towards earth with a constant acceleration I.e., a=g=9.8m/s 2 towards the earth –We’ll come back to Gravity a lot!

Physics 218, Lecture IV9 Throw a Ball up A person throws a ball upward into the air with initial velocity V 0. Calculate: The time it takes to reach its highest point (the top). Distance from her hand to the top Time to go from her hand and come back to her hand Velocity when it reaches her hand Time from leaving her hand to reach some random height h.

Physics 218, Lecture IV10 Next Week Reading: Chapter 3 Homework: –Turn in HW1 on the web by Monday at 6AM I recommend you try at least once before the weekend –Be working on HW2. Web quiz: Finish `em. Labs and Recitations: As usual… Next week: Lectures on Chapter 3: Kinematics in two dimensions and vectors