Motion in One Dimension

Velocity

Motion – A change in position

Motion

• Velocity – the rate of change in position (the time it takes to change position)

• It can be described as a “rate of motion.” • It has direction.

Usually in units such as mph, km/h, or m/s. An example of a velocity measurement would be 30mph to the east.

Velocity

What is the difference between speed and velocity?

Velocity is different from speed because speed does not specify direction, while velocity does.

Vector and Scalar quantities

• Scalar quantities have size or magnitude, but a direction is not specified.

(temperature, mass, speed, etc.)

• Vector quantities have magnitude and a specific direction (velocity, acceleration, etc.)

• Instantaneous velocity – the rate of motion at any given instant. (The car’s speedometer shows how fast the car is moving at any given instant.)

• Constant velocity – velocity that does not change or vary. (A car’s cruise control is designed to keep the car’s speed constant without the driver’s foot on the accelerator pedal.)

• Average velocity – the total displacement divided by the time interval during which it occurred.

(It takes into account that during the trip rate of change of motion may increase, decrease or stop at some points.)

• Remember: Distance is used for speed calculation, while displacement is used for velocity calculation (shortest distance between initial position and final position).

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Pg 39 Physics Serway/Faughn (Holt)

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The Physics Classroom.com

The Physics Classroom.com

Pg 40 Physics Serway/Faughn (Holt)