PHYS16 – Lecture 4
Physics of 1D Motion
September 15, 2010
Agenda
• Administration
• Key Concepts – Physics 1D motion
• Displacement, Velocity, & Acceleration
Administration
• Clickers, Textbook, Connect
• Math Exam
– Look at messages
– Due Sunday
• Homework Assignments
– Lab homework due today
– Written homework due Friday
• 2.38 – displacement not distance
• Labs – Partners…
Key Concepts: Physics 1D Motion
• Displacement, Velocity, & Acceleration
– Know the definitions of these terms
– Know how they are related
• Motion with Constant Acceleration
– Solve for constant accel. get Kinematic Eqs.
– Use the Kinematic Eqs. to solve problems
• Race Car
• Free Fall
Define Terms
Displacement
• Displacement vs. Distance
– Displacement = final position – initial position with
both magnitude and direction
– Distance = total position traversed from final
position to initial position, just magnitude
Velocity
• Velocity vs. Speed
– Velocity – final position minus initial position
divided by time, both magnitude and direction
– Speed – how fast you are going, just magnitude
60 mph
Acceleration
• Acceleration
– Final velocity minus initial velocity divided by
time, both a magnitude and a direction
– How much an object speeds up or slows down
Position graph where
acceleration is not 0
http://physics247. com
Questions: A=Yes, B=No
• Can displacement be zero and distance be
positive?
(Yes)
• Can distance ever be negative? (No)
• Can speed ever be negative?
(No)
• Can acceleration be negative? (Yes)
• Can an object that is stopped at t=0 have an
acceleration? (Yes)
• If an object is traveling at a constant velocity can
it have an acceleration?
(No)
Observe and Report – Use a Graph
Demo: Remote Control Car
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Demo: Remote Control Car
• Draw the position vs. time, velocity vs. time,
and acceleration vs. time graph for each
situation
– Constant velocity
– Constant velocity forward then constant velocity
backward
– Constant acceleration
Use Math
Demo: Determine x, v, & a
mathematically!
dt

dt

X
V
A
d
dt
d
dt
Determine v
• x=3t2 +4t -5
– v=6t+4
• a=4t2+3t+5
– v=(4/3)t3+(3/2)t2+5t+v0
– laksdj
Summary
•
•
•
•
Displacement vs. Distance
Velocity vs. Speed
Acceleration
Know how to interconvert between them!
For Next Time…
• Online lab homework due Wednesday
• Written homework due Friday
• Online Math Exam due Sunday
• Lab this week! Pick 3 partners!