-Speed and Velocity-Uniform Linear Motion

Physics

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Speed and Velocity

Average Speed= Total Distance Travelled

Time

v=d/t (Scalar)

Average Velocity= Displacement

Timev= d / t

=(d2-d1) / (t2- t1) (Vector)

Vectors and Scalars

Scalar Magnitude (size)

Vectors Magnitude and Direction

Example:

A car is travelling at an average velocity of 55km/h, N, when the driver sees a box on the road. If the reaction time of the driver is 0.45sec, how far does the car travel at that velocity before the driver even begins to break?

Instantaneous SpeedInstantaneous Velocity

Instantaneous Speed Speed at a given instant

(ex: speedometer of car)

Instantaneous Velocity Velocity at a given instant

Instantaneous speed is the magnitude of instantaneous velocity.

Note:

Average speed is equal to

the magnitude of average velocity

ONLY

when velocity is CONSTANT (magnitude and direction).

Uniform Linear Motion:

Motion with constant velocity Straight line Same direction

If the speed on this ride is constant, is the motion uniform linear motion?

Graphs of Motion: -Position-Time

-Velocity-Time-Acceleration-Time

Example: Position vs Time for Uniform Linear Motion

Time (s)

o

Position (m)

Note: The slope of the line in a Position-Time Graph equals the average velocity.

Example: Velocity vs Time for UniformLinear Motion

Time (s)

o

Velocity (m/s)

Example: Position vs Time Graph

What is the avge velocity at the time intervals: (0s-1s) (1s-1.5s) (1.5s-1.7s) (1.7s-2.0s)

Draw the velocity – time diagram.

Time, (s)

o

Position, (m)

1.00.5 1.5 2.0

20.0

10.0 A

Note:

The area under the line (curve) of a velocity-time graph is equal to the displacement of the object during that time interval.