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Explore the fundamental concepts of speed, velocity, and acceleration within a frame of reference. Learn about the differences between constant, average, and instantaneous speed, and how velocity incorporates direction. Engage in practice scenarios to solidify your understanding of these essential physics principles.
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Frame of Reference • When we describe something that is moving, we are comparing it to something that is assumed to be stationary (not moving) • Usually Earth – moves very slowly • The background or object used for comparison is called a frame of reference • For example: http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg7_relmotion/mfm05_pg7_relmotion.html
Speed • Three types of speed • Constant speed – does not vary • Average speed – distance divided by time • Instantaneous speed – the speed at a given moment • What type of speed does your car speedometer read?
Velocity • A tornado has just been sighted in Greensboro. Does the school need to go into the tornado emergency plan? • What piece of information does Mr. Telford need to make a decision? • Direction • Velocity includes both speed and direction
Speed and Velocity • Think about driving a car. Which two controls cause a change in speed? • Accelerator • Brake • Which additional control causes a change in velocity? • Steering wheel
Speed and Velocity Practice • An airplane flew 1000 km in 4 hr. What is the airplane’s speed? • A car travels 50 km west in 30 minutes. What is its velocity in km/hr? • How long will it take a ball to roll 26m if its velocity is 2.0m/s to the right? • If a runner moves with a speed of 1.5m/s and changes her speed to 2.1m/s over 3s, what is her average speed over that 3s?
Acceleration • Acceleration tells you how fast velocity is changing • Formula: A=Vf-Vi t • What are the units for acceleration? m s2 • Can be positive or negative (deceleration)
Acceleration • A car is stopped at a stoplight. When the light turns green, the car speeds up to 75 km/hr is 0.05 hr. What is the car’s acceleration rate? • Formula: A=Vf-Vi t
Acceleration • A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate? • Formula: A=Vf-Vi t
Acceleration • A car is traveling at 60 km/hr in a straight line. What is the car’s acceleration rate? • Formula: A=Vf-Vi t