HOLT PHYSICS
CHAPTER 02
MOTION IN ONE DIMENSION
I. Displacement and Velocity
Objectives:
 Describe motion in terms of frame of reference, displacement, time, and velocity.
 Calculate the displacement of an objective traveling at a known velocity for a specific
time interval.
 Construct and interpret graphs of position versus time.
A. Motion
1. One dimensional motion is the simplest type of motion.
a. Objects in one dimensional motion can move in only one direction.
2. Motion takes place over time.
3. Motion depends on a frame of reference.
B. Displacement
1. Displacement is the change in an object’s position from its original position.
a. displacement = change in position = final position-initial position
b. ∆x = xf - xi
2. Displacement
a. is not always equal to the distance traveled.
b. can be positive or negative.
c. is a vector quantity meaning that it is composed of a magnitude and direction.
C. Velocity
1. Average velocity is displacement divided by the time interval.
𝑐𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑝𝑜𝑠𝑖𝑡𝑖𝑜𝑛
𝑑𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡
a. 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 𝑐𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒 = 𝑡𝑖𝑚𝑒 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙
b. 𝑣𝑎𝑣𝑔 =
∆𝑥
∆𝑦
=
𝑥 𝑓 −𝑥 𝑖
𝑡 𝑓 −𝑡 𝑖
2. Velocity is a vector quantity meaning that it is composed of a magnitude and
direction.
3. Speed is magnitude only without direction.
4. Velocity can be interpreted graphically
𝑟𝑖𝑠𝑒
𝑐𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑐𝑜𝑜𝑟𝑑𝑖𝑛𝑎𝑡𝑒𝑠
a. 𝑠𝑙𝑜𝑝𝑒 = 𝑟𝑢𝑛 = 𝑐𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑕𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑐𝑜𝑜𝑟𝑑𝑖𝑛𝑎𝑡𝑒𝑠
b. 𝑣𝑎𝑣𝑔 =
∆𝑥
∆𝑦
=
𝑥 𝑓 −𝑥 𝑖
𝑡 𝑓 −𝑡 𝑖
c. A positive slope indicates the object is moving in a positive direction.
d. A straight line with no slope indicates the object is sitting still.
e. A negative slope indicates the object is moving in reverse or backward.
5. To find the instantaneous velocity of an object whose position – time graph is not a
straight line, a tangent is drawn to the curved line at the instant of time in question
and the slope of that line is the instantaneous velocity.
II. Acceleration
Objectives:
 Describe motion in terms of changing velocity.
 Compare graphical representations of acceleration and non-accelerated motions.
 Apply kinematic equations to calculate distance, time or velocity under conditions of
constant acceleration.
A. Changes In Velocity
1. Acceleration is the rate of change of velocity with respect to time.
𝑣 −𝑣
∆𝑣
a. 𝑎𝑎𝑣𝑔 = ∆𝑡 = 𝑡 𝑓 −𝑡 𝑖
𝑓
𝑖
𝑐𝑕𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
b. 𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑡𝑖𝑚𝑒
𝑚
𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 𝑓𝑜𝑟 𝑐𝑕𝑎𝑛𝑔𝑒
2. The unit for acceleration is 𝑠 2
𝑚 /𝑠
𝑚
1
𝑚
3. 𝑠 = 𝑠 𝑥 𝑠 = 𝑠 2
4. Acceleration is also a vector quantity meaning that it has both magnitude and
direction.
5. The velocity-time graph of an object undergoing acceleration is a pictorial
representation of what is taking place.
B. Motion With Constant Acceleration
1. Objects undergoing constant uniform acceleration experience a uniform change in
velocity over the time period in which they accelerate.
2. Therefore, the distance a uniformly accelerating object travels per unit of time also
undergoes uniform change.
3. The velocity equation can be used algebraically to solve for several other quantities.
[Board]
III. Falling Objects
Objectives:
 Relate the motion of a freely falling body to motion with constant acceleration.
 Calculate displacement, velocity, and time at various points in the motion of a freely
falling object.
 Compare the motions of different objects in free fall.
A. Free Fall
1. Free Fall is a condition in which a moving object is affected only by the acceleration
gravity.
2. The acceleration due to the gravity of Earth is -9.81 m/s2.
3. The acceleration due to gravity is the same whether an object is traveling upward or
downward.