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Calculating speed and Acceleration. Chapter 11. Speed. Speed = distance/time Velocity is speed with direction! When an object covers equal distances in equal amounts of time, it is moving at a constant speed. Instantaneous speed: speed at a given time Car Speedometer. Acceleration.
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Calculating speed and Acceleration Chapter 11
Speed • Speed = distance/time • Velocity is speed with direction! • When an object covers equal distances in equal amounts of time, it is moving at a constant speed. • Instantaneous speed: speed at a given time • Car Speedometer
Acceleration • Acceleration = (final velocity – initial velocity) time • What is true of an object’s acceleration if it is moving in a circle at a constant speed (no change in speed)? Why? • An object is moving with a constant velocity. What is the objects acceleration?
Calculating Speed • To calculate speed, you must measure two quantities: thedistancetraveled and the timeit took to travel that distance. • Average Speed: • SI unit for speed: meters per second (m/s)
Let’s Practice!!! • Find the velocity in meters per second of a swimmer who swims 110 m toward the shore in 72 s.
Let’s Practice! • A train travels 225 kilometers in 2.5 hours. What is the train’s average speed?
You Try It! • An airplane travels 3,260 kilometers in 4 hours. What is the airplane’s average speed? • A person in a kayak paddles down river at an average speed of 10 km/h. After 3.25 hours, how far has she traveled?
Calculating Acceleration • To calculate acceleration, you must measure three quantities: the initial velocity, final velocity and time it took to change velocities. • Average Acceleration: • SI unit for Acceleration: meter per second per second (m/s^2) • NOTE: Rest in word problems => v = 0 m/s (could be final or initial depending on situation)
Let’s Practice!!! • Bob is at a stop light and then speeds up to 60 miles/hr. It takes Bob 1 hour to go from rest to 60 miles/hr. What is his acceleration?
Mr. Terrell drops (starts from rest) a water balloon from the top of a building onto a football player at the ball game. If the acceleration is -9.8 m/s2 and it takes the 10 s to reach the football player, what is the final velocity of the balloon?
James while on his skateboard experiences a constant acceleration of 1 m/s2 for 2 seconds until he reaches a speed of 20 m/s. What is his initial velocity?
A ball experiences an acceleration of -3 m/s2. It goes from 30 m/s to 14 m/s. How long does it take the ball to slow down?
You Try It! • A skater goes from a standstill to a speed of 6.7 m/s in 12 seconds. What is the acceleration of the skater? • During a race, a sprinter increases from 5.0 m/s to 7.5 m/s over a period of 1.25s. What is the sprinter’s average acceleration during this period?
a a b b c c d d Distance (m/s) Speed (m/s) Time (s) Time (s) Graphing Review • Describe the following graphs:
Finding Slope Example • Slope from 0 - 5 seconds? • Slope from 5 – 10 seconds?
Units of slope on a position vs. time graph? SLOPE (on position vs. time graph) = ____________ Units of slope on a speed vs. time graph? SLOPE (on velocity vs. time graph) = _____________
Exit Slip • You ride your bike for a distance of 30 km. You travel at a speed of 0.75 km/ minute. How many minutes does this take?
Warm-Up • Calculate the distance a plane flies on an 8 hour flight from Chicago to London. Assume a constant speed of 800 km/h.