Linear Motion PowerPoint Presentation, PPT - DocSlides

Linear Motion

Motion is relativeAn object’s motion is always described in reference to another object

Relative Motion

When an object is said to be traveling at 60 km/h (or at any speed), it is implied that it is moving at 60 km/h relative to the Earth.

Relative Motion

Jamiroquai “Virtual Insanity” Travelling Without Moving 1997 Video of the Year

Relative Motion

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Vector- a quantity possessing both magnitude and directionScalar- a quantity possessing only magnitude

Vectors and Scalars

Examples of Vectors: Displacement (Δx)Velocity (v)Acceleration (a)Force (F)Momentum (p)

Vectors and Scalars

Examples of Scalars: Distance (d)Mass (m)Speed (v)Time (t)

Vectors and Scalars

Instantaneous speed: the speed that something has at any one instanceAverage speed: the speed of an object over a time interval

Speed

Speed

The average speed for a trip might be 53 miles/hour.

...or 70 miles/hour on the open road.

However, during this trip your

instantaneous speed

might have been 0 miles/hour at a stoplight...

Speed

What are the units of speed?

miles/hour…………….mph

kilometer/hour……….km/h

meters/second……….m/s

furlongs/fortnight?

Speed

1. What is the average speed of a cheetah that sprints 100 meters in 4 seconds?

2. How about if it sprints 50 m in 2 s?

Velocity

Velocity

= {speed with a direction}

Examples:

70 mph

is a

speed

.

70 mph North

is a

velocity

.

Velocity

What are the units of velocity?

Velocity has the same units as speed except they also have a direction

Velocity and speed equations

Velocity vs. speed

The speedometer of a car moving to the east reads 100km/h. It passes another car that moves to the west at 100km/h.

Do both cars have the same speed?

Do they have the same velocity?

In an unusual move by the New York State Department of Transportation, all of the "speed limit" signs were replaced with "velocity limit" signs. What would such a sign look like? How could one travel faster than the old speed limit without violating the new velocity limit?

Conceptual Review

Which device(s) on a car can be used to change … its speed? its velocity but not its speed?

Conceptual Review

A car driving on a circular test track shows a constant speedometer reading of 100 kph for one lap. Describe the car's speed during this time. Describe its velocity. How do the speed and velocity compare?

Conceptual Review

Is it possible for an object to have … constant speed and changing velocity, changing speed and constant velocity?

Conceptual Review

Why are the devices in cars called speedometers and not velocitometers?

Conceptual Review

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Relative Motion…one more time

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Acceleration

Acceleration is the rate of change of velocity.

Acceleration

What are the units of acceleration?

miles/hour/second…………….mi/h/s

kilometer/hour/second……….km/h/s

meters/second/second……….

m/s/s or m/s

2

Acceleration equations

Acceleration

Acceleration is the

positive or negative depending on the direction of the acceleration.

Acceleration

An object traveling with a constant positive velocity

Acceleration

An object traveling with a constant negative velocity

Acceleration

An object traveling with a positive velocity, positive acceleration.

Acceleration

An object traveling with a positive velocity, negative acceleration.

Acceleration

An object traveling with a negative velocity, negative acceleration.

Acceleration

An object traveling with a negative velocity, positive acceleration.

Graphs of Motion

On a displacement vs. time graph the slope of the line is equal to the velocity of the object.

On a velocity vs. time graph the slope of the line is equal to the acceleration of the object.

O

n a

velocity vs. time

graph the area underneath the curve is equal to the

displacement

of the object.