Transcript Physics for the Life Sciences I

Motion in One Dimension
Kinematics
Dynamics vs. Kinematics
• Dynamics – motion related to __________
• Kinematics – describes motion
______________ without regard to cause
or force
Frame of Reference
•
Specify an ______
For 1-D motion the coordinate system is
______
x
x=0
Time and Space
• Instant ≡ particular ______ in time
• Interval ≡ ________ between two instants
 t  t f  ti
• Position ≡ particular ______ in space
• Displacement ≡ __________ between two
positions
 x  x f  xi
Vectors vs. Scalars
• Vectors – indicate magnitude and ______
– Boldfaced and/or vector sign
Displacement
Velocity
Acceleration

x

v

a
• Scalars – indicate __________ only
Distance
Speed
Magnitude of
acceleration

x  x

v v

a  a
Displacement is a Vector
Fig. 2.2, p. 25
For 1-D, vector nature is indicated by ______sign
Displacement
1. Change in _________ is called
displacement
The sign tells us if displacement is
towards _______ or ________ values
 x  x f  xi
2.1 
Average Velocity
2. Displacement divided by _____ interval
The ____ tells us if object is moving
toward positive or negative values
v 
x
t

x f  xi
t f  ti
2.2 
Instantaneous Velocity
3.
The average velocity when the time
interval approaches _____
It is the ______ of the line of a position
versus time graph
v  lim
t 0
x
t
2.3 
Instantaneous Velocity – Graphical
Interpretation
What is v at t = 4 s?
Average Acceleration
4. The change in velocity over a
_______________
a 
v
t

v f  vi
t f  ti
2.4 
Instantaneous Acceleration
5. The average acceleration when the time
interval approaches _____
It is the ______ of a velocity versus time
graph
a  lim
 t 0
v
t
2.5 
Signs of v and a
v
a
Object is:
+
+
speeding up
+
–
slowing down
–
+
slowing down
–
–
speeding up
Graphical Interpretation
Red
Blue
Green
1. Rank the velocities in decreasing order.
2. Find numerical values for the velocities.
3. Rank the speeds in decreasing order.
Graphical Interpretation (cont’d)
Red
Green
1. Are the velocities constant?
2. Which has the larger acceleration?
Types of Motion
• Uniform Motion: v = ________, a = ______
• Nonuniform Motion
– Uniform acceleration: a = _________
– Nonuniform acceleration: a is _____ constant