Lecture 01: 1D Kinematics Physics 2210 Fall Semester 2014
Lecture 01: 1D Kinematics
Physics 2210Fall Semester 2014
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Alles Leben ist Problemlösen
- Karl Popper
“Supplemental Readings” link on course webpage:
I will post Main Points for each SP
Chapter
“Supplemental Readings” link on course webpage:
Equation Sheet
Help Lab Schedule(JFB Rotunda)
Monday 09:00 – 11:00 AM Amaya
Tuesday 12:00 – 01:00 PM Nick
Wednesday 09:30 – 11:30 AM Jason
Thursday 12:00 – 01:00 PM Nick
02:00 – 03:00 PM Mei
Friday 02:00 – 03:00 PM Mei
Also will be posted to course web page
Unit 1 Feedback
● Thanks for your comments!
● Main points:● Definition of
acceleration, esp. negative acceleration.
● Interpreting graphs● Checkpoint #2● Calculus practice● Examples
Kinematics: n. The branch of mechanics that studies the motion of a body or a system of
bodies without consideration given to its mass or the forces acting on it.
www.thefreedictionary.com
Mechanics Lecture 1, Slide 7
Today's Concepts:a) Displacement, Velocity, Accelerationb) 1-D Kinematics with constant acceleration
Mechanics Lecture 1, Slide 8
Displacement and Velocity in One Dimension
Displacement, time interval finite
Displacement, time interval infinitesimal
Flashcard Questions
Mechanics Lecture 1, Slide 10
A) YESB) NO
Are the plots shown at the left correctly related?
Displacement and Velocity in One Dimension
Mechanics Lecture 1, Slide 11
A) YESB) NO
Are the plots shown at the left correctly related?
Displacement and Velocity in One Dimension
Mechanics Lecture 1, Slide 12
The velocity vs. time plot of some object is shown to the right.
Which diagram below could be the Displacement vs. time plot for the same object?
A B C
Mechanics Lecture 1, Slide 13
The velocity vs. time plot of some object is shown to the right.
Which diagram below could be the Displacement vs. time plot for the same object?
A B C
Mechanics Lecture 1, Slide 14
Acceleration
For the Displacement and Velocity curves shown on the left, which is the correct plot of acceleration vs. time?
AA
BB
Checkpoint 1:
Mechanics Lecture 1, Slide 16
AA
BB
The object slowed down (negative acceleration) and at the midpoint sped up (positive acceleration).
Acceleration is negative while the velocity decreases and it is positive as the velocity increases
Typical B answers
Checkpoint #1 Results
Mechanics Lecture 1, Slide 17
Constant Acceleration
constanta(t) = a
Example
a) Plot a graph of the acceleration vs time
b) Determine the average acceleration for 5 s < t < 15 s and
c) for 0 < t < 20 s.
A velocity-time graph for an object moving along the x axis is shown in the figure.
Mechanics Lecture 1, Slide 18
Suggested Problem Solving Template
1) Keep calm, and...
2) Read the problem carefully.
3) Draw a diagram w/ coordinates.
4) List knowns.
5) List unknowns.
6) Find equation linking knowns & unknowns.
7) Solve the equation.
8) Repeat as needed.
Mechanics Lecture 1, Slide 20
At t = 0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. Suppose it moves 1 foot between t = 0 sec and t = 1 sec.
How far does it move between t = 1 sec and t = 2 sec?
A) 1 foot B) 2 feet C) 3 feet D) 4 feet E) 6 feet
Checkpoint 2
Mechanics Lecture 1, Slide 21
1ft4ft
9ft
3'
16ft
At t = 0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. Suppose it moves 1 foot between t = 0 sec and t = 1 sec.
How far does it move between t = 1 sec and t = 2 sec?
A) 1 foot B) 2 feet C) 3 feet D) 4 feet E) 6 feet
Checkpoint 2
Mechanics Lecture 1, Slide 22
1ft4ft
9ft
3'
16ft
At t = 0 a ball, initially at rest, starts to roll down a ramp with constant acceleration. Suppose it moves 1 foot between t = 0 sec and t = 1 sec.
How far does it move between t = 1 sec and t = 2 sec?
A) 1 foot B) 2 feet C) 3 feet D) 4 feet E) 6 feet
Checkpoint 2
Mechanics Lecture 1, Slide 23
Acceleration is one foot per second, using displacement equation with accel as a constant gives us x = 0+0+.5*1*2^2 = 2
The ball has an acceleration of 1ft/s^2. So, for every second that the ball is moving, it gains another 1ft/s of velocity.
Typical B answers
1ft4ft
9ft
3
16ft
Checkpoint 2 Responses
Checkpoint 2 Follow-up
The ball is now rolled up the same ramp. It is given an initial speed of 10 feet/second. How far will it roll before stopping, and then rolling back down the ramp? Ans: 25 feet
Example
A hare and a tortoise race over a straight course, 1.00 km long. The tortoise crawls at a speed of 0.200 m/s toward the finish line. The hare runs at a speed of 8.00 m/s toward the finish line for 0.800 km and then stops while the tortoise passes. The hare then resumes running at 8.00 m/s, and the hare and the tortoise cross the finish line at the same time.
a) How far is the tortoise from the finish line when the hare resumes running?
b) For what time interval was the hare stationary?
a) 25 metersb) 4,875 seconds
Example
A ball is thrown upwards with an initial speed of 3.0 meters/second. How far will it rise before it comes to rest, and then falls back down?
(Assume the acceleration due to gravity g = 9.81 m/s2, and negligible air resistance.)
0.459 meters