Motion

Chapter 11Page 328-348

Distance and Displacement

Chapter 11 Section 1Pg. 328-331

Distance and Displacement

• To describe_________ , you must state the direction the object is moving as well as how fast the object is moving. You must also tell its ________ at a certain time.

Choosing a Frame of Reference

• ________________: a system of objects that are not moving with respect to one another; it is the necessary ingredient of a description of motion

• Must answer these 2 questions…– ___ fast are you moving?– Which _____ should you choose?

Choosing a Frame of Reference

How fast are you moving?• Relative motion: movement in ________ to a

frame of reference• Example: as a train moves past a platform,

people standing on the platform will see those on the train speeding by. But when the people on the train look at one another, they don’t seem to be moving at all.

Choosing a Frame of Reference

Which frame should you choose?• Example: If on a train, looking at a treetop will

help you see how fast you are moving relative to the ground. If you are walking on the train, then looking at a seat will help you see how fast you are moving relative to the train.

Measuring Distance

• Distance: the ______ of a path between two points.

• SI unit of measure= meter (m)• For very long distances, _________ (km) is

used• 1 km = 1,000 m• Small distances, __________ (cm)

Measuring Displacements

• ______________ provides this information: – Distance is the length of the path between two

points. – Displacement is the ________ from the starting

point and the length of a straight line from the starting point to the ending point.

• Displacement is sometimes used when giving directions.

Combining Displacements

• Displacement is an example of a ______.• Vector: a quantity that has magnitude and

direction– _________ can be size, length, or amount– Represented on a map by arrows– The length of the arrow shows the magnitude of the

vector.– Vector _______ is the combining of vector

magnitudes and directions. Add displacements using vector addition.

Combining Displacements

Displacement Along a Straight Line• When 2 displacements, represented by two

vectors, have the _______ direction, you can _____ their magnitudes

• When 2 displacements have the ________ direction, you can _________ their magnitudes

Combining Displacements

Displacement That Isn’t Along a Straight Path• When 2 or more displacement vectors have

________ directions, they may be combined by graphing.

• See Figure 4 on page 331• ______________: (vector in red) the vector

sum of two or more vectors

Speed and Velocity

Chapter 11 Section 2Page 332-337

Speed

• _____: the ratio of the distance an object moves to the amount of time the object moves.

• SI unit= meters per second (m/s)– However, choose units that make the most sense

for the motion you are describing• 2 ways to express the ______ of an object are

average speed (computed for the entire duration of a trip) and instantaneous speed (measured at a particular instant)

Speed

Average Speed• ____________, ν, is the total distance

traveled, d, divided by the time, t, it takes to travel that ________

Math Practice

• See page 333• Do #1-2

Speed

Instantaneous Speed• How ___ you are going at a particular moment• This is what your car’s speedometer gives you• ____________ speed, ν, is the rate at which

an object is moving at a given moment in time

Graphing Motion• To describe _______- a distance-time graph

should be used• The _____ of a line on a distance-time graph

is speed.– Slope of straight portions represent periods of

constant speed– ______ represent a gradual increase or decrease

in speed– Steeper slope means a ______ speed

• See page 334 in book

Velocity

• Together, the speed and direction in which an object is moving are called ________

• Velocity is a description of both speed and direction of motion.

• Velocity is a ______.– Longer vector represents a faster speed– Shorter vector represents a slower speed– Uniform motion is another way of saying constant velocity

• A ______ in velocity can be the result of a change in speed, a change in direction, or both

Combining Velocities

• Two or more velocities add by vector addition

• See page 337, Figure 10 in book

Acceleration

Chapter 11 Section 3Page 342-348

What is Acceleration?

• ____________: the rate at which velocity changes

• Acceleration can be described as changes in speed, changes in direction, or changes in both

• Acceleration is a ______

What is Acceleration?

Changes in Speed• Acceleration is often used to describe

situations in which the _____ of an object is ________.

• Scientifically, acceleration applies to any change in an object’s _______. The change may be either and increase (positive) or a decrease (negative) in speed

What is Acceleration?

• See example in your book– Page 343 (2nd paragraph, also figure 12)

• An example of acceleration due to a change in speed is __________– The movement of an object toward Earth solely

because of _______.– Units are meters per second squared (m/s2)– Objects falling near Earth’s _______ accelerate

downward at a rate of 9.8 m/s2

What is Acceleration?

Changes in Direction• Acceleration may still occur when speed is

__________.– Example: you experience acceleration when you

ride your bicycle around a curve• Even if you have constant ______, change in

direction means you are accelerating.

What is Acceleration?Changes in Speed and Direction• _______ is characterized by both changes in

speed and direction at the ____ time• Think about a ride on a roller coaster…– Acceleration is constantly ________ because of changes in the speed and direction of the cars on the roller coaster.

What is Acceleration?

Constant Acceleration

• Constant Acceleration- a steady ______ in velocity

• The velocity of an object moving in a _______ ______ changes at a constant rate when the object is experiencing constant acceleration

Calculating Acceleration

• Acceleration for straight-line motion

a= change in velocity or total time

– Velocity ________: acceleration will be negative– Velocity increases: acceleration will be _______

Calculating Acceleration

• See worked example on page 346• Work problems 1-4 on page 346

Graphs of Accelerated Motion

• ______ can be used to calculate acceleration• The slope of a speed-time graph is

acceleration

Graphs of Accelerated Motion

Speed-Time Graphs• Constant _________ is represented on a

speed-time graph by a straight line• Linear graph- displayed data form straight-line

parts; the ______ is acceleration• See example graphs– Pg. 347

Graphs of Accelerated Motion

Distance-Time Graph• Accelerated motion is represented by a _____

line on a distance-time graph – (example: pg. 348)

• Nonlinear graph- a curve connects the data points that are ______

• Increasing slope = increasing ______

Instantaneous Acceleration

• Acceleration is ______ constant• Motion is rarely in a straight line• Instantaneous __________ is how fast a

velocity is changing at a specific instant.• Remember: acceleration involves a change in

velocity or direction or _____

Works Cited

Frank, Wysession, & Yancopoulos. “Chapter 11 Motion.” Physical Concepts in Action. Upper Saddle River: Pearson, 2010. 328-349. Print.