Motion in One Dimension

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# Motion in One Dimension - PowerPoint PPT Presentation

Motion in One Dimension. Motion in One Dimension. Movement along a straight-line path  Linear motion Convenient to specify motion along the x and y coordinate system. Motion in One Dimension. Important to specify magnitude &amp; direction of motion (Up or down; North, South, East, or West)

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## PowerPoint Slideshow about 'Motion in One Dimension' - luce

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Presentation Transcript
Motion in One Dimension
• Movement along a straight-line path Linear motion
• Convenient to specify motion along the x and y coordinate system
Motion in One Dimension

Important to specify magnitude & direction of motion (Up or down; North, South, East, or West)

• Coordinate (x and y) axes
• Objects right of origin on x axis = positive
• Objects left of origin on x axis = negative
• Objects above origin on y axis = positive
• Objects below origin on y axis = negative

POSITION:

• Location of an object relative to an origin
Displacement versus Distance
• Displacement (x)
• Distance & direction
• Measures net change in position
• Displacement may not equal total distance traveled
Distance
• Distance
• Total path length traversed in moving from one location to another
• Example: Jimmy is driving to school but he forgets to pick up Johnny on the way…He now has to reverse his direction and drive back 2 miles
• Total Distance Traveled = 12 miles
• Total Displacement = 8 miles

- 2 miles

+ 10 miles

Vector

Quantity with both magnitude and direction

* Represented by arrows in diagrams

Velocity

Average velocityis the displacement divided by the elapsed time.

Speed versus Velocity
• Speed:
• Positive number, with units
• Does not take into account direction
• Speed is therefore a _ _ _ _ _ _ quantity?
• Velocity (v):
• Specifies both the magnitude(numerical value  how fast an object is moving) and also the direction in which an object is moving
• Velocity is therefore a _ _ _ _ _ _ quantity?
Average Velocity

The football player ran 50 m in 20 s. What is his average velocity?

v = 50 m / 20 s = 2.5 m/s

Velocity

The World’s Fastest Jet-Engine Car

Andy Green in the car ThrustSSC set a world record of

341.1 m/s (762.8 mph) in 1997. To establish such a record, the driver makes two runs through the course, one in each direction, to nullify wind effects. From the data, determine the average velocity for each run.

Velocity

(759 mph)

(766.4 mph)

Acceleration
• Acceleration (a)
• Change in velocity per time interval

Animation of constant acceleration website

Acceleration

Acceleration and Decreasing

Velocity

Acceleration
• Acceleration:
• Vector quantity 
• Positive acceleration
•  Velocity increasing
• Negative acceleration
•  Velocity decreasing
• SI units for acceleration:
• meters/second2  m/s2

Acceleration Animation Website

Animation - Direction of Acceleration and Velocity Website

Motion Equations for Constant Acceleration
• Constant Acceleration:
• Instantaneous & average accelerations are equal
Variables

1. Displacement  x (meters)

2. Acceleration (constant) a (m/s2)

3. Final velocity  v (m/s)

4. Initial velocity  vo (m/s)

5. Elapsed time  t (s)

Motion Equations for

Constant Acceleration

Solving Problems
• Draw a depiction of the situation
• Utilize x and y coordinate axes with +/- directions
• Write down known variables
• Select appropriate equation
• Complete calculation
• **UNITS!
• Reasonable result?

Example: Catapulting a Jet

** Find its displacement.

An Accelerating Spacecraft

A spacecraft is traveling with a velocity of +3250 m/s. Suddenly the retrorockets are fired, and the spacecraft begins to slow down with an acceleration whose magnitude is 10.0 m/s2. What is the velocity of the spacecraft when the displacement of the craft is +215 km, relative to the point where the retrorockets began

firing?

Falling Objects
• Galileo Galilei’s Contribution
• In the absence of air resistance, all objects on Earth fall with the same constant acceleration.
• Acceleration due to gravity (g) = 9.8m/s2
Free-fall
• Any freely falling object being acted upon solely by the force of gravity
• Ignore air resistance
• Rate of acceleration due Earth’s gravity
• g = 9.8 m/s2
• Vector 
• Direction is towards the center of the Earth
Free Fall
• Object does not have to be falling to be in free fall
• Example - Throwing a ball upward  Motion is still considered to be free fall, since it is moving under the influence of gravity

Acceleration due to Gravity Equations

Constant Acceleration

Equations

A Falling Stone

A stone is dropped from the top of a tall building. After 3.00s of free fall, what is the displacement y of the stone?

How High Does it Go?

The referee tosses the coin up

with an initial speed of 5.00m/s.

In the absence of air resistance,

how high does the coin go above

its point of release?