Speed, Velocity, and Speed, Velocity, and Acceleration ReviewAcceleration Review

Frame of ReferenceFrame of Reference

When we describe something that is When we describe something that is moving, we are comparing it to something moving, we are comparing it to something that is assumed to be stationary (not that is assumed to be stationary (not moving)moving)Usually Earth – moves very slowlyUsually Earth – moves very slowly

The background or object used for The background or object used for comparison is called a comparison is called a frame of referenceframe of reference

For example: For example: http://www.classzone.com/books/ml_science_share/vis_sim/mfm05http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg7_relmotion/mfm05_pg7_relmotion.html_pg7_relmotion/mfm05_pg7_relmotion.html

SpeedSpeed

Three types of speedThree types of speedConstant speed – does not varyConstant speed – does not varyAverage speed – distance divided by Average speed – distance divided by

timetimeInstantaneous speed – the speed at a Instantaneous speed – the speed at a

given momentgiven momentWhat type of speed does your car What type of speed does your car

speedometer read?speedometer read?

VelocityVelocity

A tornado has just been sighted in A tornado has just been sighted in Greensboro. Does the school need to go Greensboro. Does the school need to go into the tornado emergency plan?into the tornado emergency plan?What piece of information does Mr. What piece of information does Mr.

Telford need to make a decision?Telford need to make a decision?DirectionDirection

Velocity includes both speed and directionVelocity includes both speed and direction

Speed and VelocitySpeed and Velocity

Think about driving a car. Which two Think about driving a car. Which two controls cause a change in speed?controls cause a change in speed?AcceleratorAcceleratorBrakeBrake

Which additional control causes a change Which additional control causes a change in velocity?in velocity?Steering wheelSteering wheel

Speed and Velocity PracticeSpeed and Velocity Practice

An airplane flew 1000 km in 4 hr. What is An airplane flew 1000 km in 4 hr. What is the airplane’s speed?the airplane’s speed?

A car travels 50 km west in 30 minutes. A car travels 50 km west in 30 minutes. What is its velocity in km/hr?What is its velocity in km/hr?

How long will it take a ball to roll 26m if its How long will it take a ball to roll 26m if its velocity is 2.0m/s to the right?velocity is 2.0m/s to the right?

If a runner moves with a speed of 1.5m/s If a runner moves with a speed of 1.5m/s and changes her speed to 2.1m/s over 3s, and changes her speed to 2.1m/s over 3s, what is her average speed over that 3s?what is her average speed over that 3s?

AccelerationAcceleration

Acceleration tells you how fast velocity is Acceleration tells you how fast velocity is changingchanging

Formula:Formula:

A=A=VVf-V-Vi

ttWhat are the units for acceleration?What are the units for acceleration?mmss22

Can be positive or negative (deceleration)Can be positive or negative (deceleration)

AccelerationAcceleration

A car is stopped at a stoplight. When the A car is stopped at a stoplight. When the light turns green, the car speeds up to 75 light turns green, the car speeds up to 75 km/hr is 0.05 hr. What is the car’s km/hr is 0.05 hr. What is the car’s acceleration rate?acceleration rate?

Formula:Formula:

A=A=VVf-V-Vi

tt

AccelerationAcceleration

A car is traveling at 60 km/hr in a straight A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate?line. What is the car’s acceleration rate?

Formula:Formula:

A=A=VVf-V-Vi

tt

AccelerationAcceleration

A car is traveling at 60 km/hr in a straight A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate?line. What is the car’s acceleration rate?

Formula:Formula:

A=A=VVf-V-Vi

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