Mechanics Lecture 1, Slide 1 1d -Kinematics-summary Main points of 1d-kinematics again Hints on doing homework Homework Examples Homework Deadline extended (Sunday 1/25 11:30PM)

Main Points of Unit 1 Mechanics Lecture 1, Slide 2

Main Points of Unit 1 Mechanics Lecture 1, Slide 3

1d-Kinematic Equations for constant acceleration Mechanics Lecture 1, Slide 4  Basic Equations to be used for 1d – kinematic problems.  Need to apply to each object separately sometimes with time offset  When acceleration changes from one constant value to another say a=0  The problem needs to be broken down into segments

Homework Hints Start Early and allow yourself enough time Write out solutions on paper BEFORE entering answers online Ensure that stated problem is understood Identify the useful equations Identify the information to be used Sometimes the required information is not stated explicitly Make diagrams and rough graphs of quantities Break the problem up into parts Solve algebraically first Check that equations are reasonable Carefully perform calculations Stay calm… Mechanics Lecture 1, Slide 5

Interactive Example V vs T Mechanics Lecture 1, Slide 6 ?

Interactive Example V vs T Mechanics Lecture 1, Slide 7 Region 1: 0<t<1.5 s Region 2: 1.5s<t<3.0s Region 3: 3.0s<t<5.0s Region 1 Region 2 Region 3 What happened in region 3? Smartphysics Conclusion

I-74 problem Mechanics Lecture 1, Slide 8

I-74 problem Mechanics Lecture 1, Slide 9 Facts Equations Where are the cars when they meet?The same place Solve for meeting time Where was Chuck when Anna passed prospect avenue? Express meeting time in terms of separation of Chuck and Anna at t=0: Solve for meeting time and location Be careful with your facts!

I-74 Problem Mechanics Lecture 1, Slide 10 x t Anna Chuck t meet x a0 tdtd x c0 x c (t=t d )

Car-ride problem Mechanics Lecture 1, Slide Yellow car Blue car

Car-ride problem Mechanics Lecture 1, Slide 12 Gather facts And equations

Car-ride problem Mechanics Lecture 1, Slide 13

Quadratic Equation-which solution Mechanics Lecture 1, Slide 14 t

Two thrown balls problem Mechanics Lecture 1, Slide 15

Two thrown balls problem Mechanics Lecture 1, Slide 16 Facts

Two thrown balls problem Mechanics Lecture 1, Slide 17 SAME HEIGHT  MEET Use relevant kinematic equations Simplify equation Solve for t meet

Two thrown balls problem-Alternative Solution Mechanics Lecture 1, Slide 18 Use equation relating velocity and position to solve for height Then solve for time at maximum height Continue solving the rest of the problem as before…

The meeting Problem in General Mechanics Lecture 1, Slide 19 Whenever possible solve symbolically. Then plug in the numbers!!!! You can understand what is going on better if you keep the equations organized. Define your problem; Identify useful equations Start solving… Gather terms…Does the equation look reasonable? Solve for desired quantity… Position of object 1 when object 2 is launched Speed of object 1 when object 2 is launched This time is w.r.t object 2. To obtain time w.r.t object 1 need to add delay time

Two thrown balls problem #2 Mechanics Lecture 1, Slide 20

Two thrown balls problem #2 Mechanics Lecture 1, Slide 21 Position of object 1 at moment object 2 is launched Velocity of object 1 at moment object 2 is launched Use your equation in symbolic form and gather the values to be used…. Solve for individual elements of equation…can check if things make sense Solve for displacement and relative velocity at time when object 2 launches Divide to obtain time when objects meet Note that acceleration term after 2 nd object is released drops out!!!

Two thrown balls problem #2 Mechanics Lecture 1, Slide 22

Schaum’s Outline Mechanics Lecture 1, Slide 23

Displacement,Velocity & Acceleration Mechanics Lecture 1, Slide 24 Need to become comfortable with displacement, velocity and acceleration and how they are related!!!

Constant Acceleration Mechanics Lecture 1, Slide 25

Mechanics Lecture 1, Slide 26

Hyperphysics-Motion Mechanics Lecture 1, Slide 27

Hyperphysics-Motion Mechanics Lecture 1, Slide 28

Hyperphysics Motion Mechanics Lecture 1, Slide 29 Displacement vs timet Velocity vs timet Acceleration vs timet

Hyperphysics Motion Mechanics Lecture 1, Slide 30

Enter Question Text A. True B. False Mechanics Lecture 1, Slide 31 I experienced some degree of “frustration” with the Homework Problems

Enter Question Text A. True B. False Mechanics Lecture 1, Slide 32 I experienced a sense of “accomplishment” solving the Homework Problems