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Metric Prefixes Practice

Metric Prefixes Practice. If a radio wave has a period of 1 µs, what is the period in seconds? A hydrogen atom has a diameter of about 10 nm. Express this diameter in meters. Express this diameter in millimeters. Express this diameter in micrometers.

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Metric Prefixes Practice

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  1. Metric Prefixes Practice • If a radio wave has a period of 1 µs, what is the period in seconds? • A hydrogen atom has a diameter of about 10 nm. • Express this diameter in meters. • Express this diameter in millimeters. • Express this diameter in micrometers. • The distance between the sun and Earth is about 1.5 X 1011 m. Express this distance in kilometers and gigameters.

  2. Frame of Reference • A system that defines where objects are for a problem. • For certain problems, there may be multiple frames of reference that can be used.

  3. Scalar Vs. Vector • Scalar • Vector

  4. Displacement • Similar to distance, but displacement will also include the direction traveled. • Direction is indicated by a positive or negative number. • Positive means right or up and negative means left or down. • Equation: Δx=xf-xi • Units:

  5. Velocity • Similar to speed, but velocity also includes the direction traveled. • We will calculate average velocity using the equation, = • The sign conventions that we used for displacement also work for velocity. • Units:

  6. Average Velocity Example • During a race on level ground, Andra runs with an average velocity of 6.02 m/s east, what is her displacement after 137 s?

  7. Average Velocity Problems • Heather and Matthew walk with an average velocity of 0.98 m/s east. If it takes them 34 minutes to walk to the store, what is their displacement? • If Joe rides his bicycle in a straight line for 15 minutes with an average velocity of 12.5 km/hr south, how far has he ridden?

  8. Problems Continued • Simpson drives his car with an average velocity of 48.0 km/hr east. How long will it take him to drive 144 km on a straight road? • A bus travels 280 km south along a straight path with an average velocity of 88 km/hr south. The bus stops for 24 minutes. Then, it travels 210 km south with an average velocity of 75 km/hr south. How long does the total trip last? What is the overall average velocity?

  9. Instantaneous Velocity • Instantaneous velocity can be found on a position vs. time graph. • It is the velocity at a given point in time. • It is found by finding the slope of the tangent line at that point of the graph. • Tangent line-

  10. What is the instantaneous velocity at 1s, 3s, 4.2s and 7.3s?

  11. Acceleration • Defined as the rate in change of velocity • It could be a change in speed and/or direction • The following equation allows us to calculate average acceleration: • = • Unit for acceleration:

  12. Velocity and Acceleration

  13. Average Acceleration Example • A shuttle bus slows down with an average acceleration of -1.8 m/s2. How long does it take the bus to slow from 9.0 m/s to a complete stop?

  14. Average Acceleration Problems • A car traveling at 7.0 m/s accelerates uniformly at 2.5 m/s2 to reach a speed of 12.0 m/s. How long does this take? • With an average acceleration of -1.2 m/s2, how long will it take to bring a bicycle at a speed of 6.5 m/s to a complete stop?

  15. Problems Continued • Turner’s treadmill runs with a velocity of -1.2 m/s and speeds up at regular intervals during a half-hour workout. After 25 min, the velocity is -6.5 m/s. What is the average acceleration during this period? • Suppose a treadmill has an average acceleration of 4.7X10-3 m/s2. How much will the speed change after five minutes? If the initial speed is 1.7m/s, what is the final speed?

  16. Displacement With Constant Acceleration • We will use several equations that include displacement, velocity, acceleration and time. • The first is below:

  17. Example • A racing car reaches a speed of 42 m/s. It undergoes a constant acceleration and comes to a rest 5.5 s later. How far did the car take to stop?

  18. Problems • A car accelerates uniformly from rest to a speed of 6.6 m/s in 6.5 s. Find the distance. • A driver in a car traveling at a speed of 21.8 m/s sees a cat 101 m away on the road. How long will it take for the car to accelerate uniformly to rest in 99 m. • A car enters the freeway with a speed of 6.4 m/s and accelerates for 3.2 km in 3.5 min. How fast is the car moving at the end?

  19. Velocity and Displacement With Constant Acceleration • You will use these equations when given the acceleration.

  20. Example • A plane at rest accelerates at 4.8 m/s2 for 15 seconds and takes off. What is the speed at takeoff? How long must the runway be?

  21. Problems • A car with an initial speed of 6.5 m/s accelerates at a uniform rate of 0.92 m/s2 for 3.6 s. Find the final speed and displacement. • An automobile with an initial speed of 4.3 m/s accelerates at 3.0 m/s2. Find the final speed and displacement after 5.0 seconds.

  22. Problems Continued • A car starts from rest and travels for 5.0 s with an acceleration of -1.5 m/s2. What is the final velocity? How far does it travel? • A car traveling at 15 m/s applies the brakes and accelerates at -2.0 m/s2. How long does it take to accelerate to 10 m/s? How far did the car travel?

  23. Final Velocity After Any Displacement • This equation can be used when we don’t know the time. • Magnitude-

  24. Example • A person pushing a stroller starts from rest and accelerates at 0.5 m/s2. What is the velocity after 4.75 m?

  25. Problems • A car traveling at 7.0 m/s accelerates at 0.8 m/s2 for 245 m. What is the final velocity? What is the velocity after 125 m? • A car accelerates from rest at a rate of 2.3 m/s2. What is the speed after 55 m? How long does it take to travel 55 m?

  26. Problems Continued • An aircraft has a liftoff speed of 33 m/s. What minimum acceleration does this require if the plane lifts off after 240 m? • A certain car is capable of accelerating at 0.85 m/s2. What is the magnitude of the car’s displacement as it accelerates from 83 km/hr to 94 km/hr?

  27. Mixed Problems • Nathan accelerates his skateboard from rest to 12.5 m/s in 2.5 s. • What is his acceleration? • What is his displacement? • What is his average velocity? • Marissa’s car accelerates at a rate of 2.6 m/s2 how long does it take to go from 24.6 m/s to 26.8 m/s?

  28. Free Fall • An object in free fall is falling toward the Earth and the only force acting on it is gravity. • Every object experiences the same acceleration due to gravity. • g= • Also, since the acceleration is downward, g will be negative. • The acceleration is the same for an object going straight up.

  29. Free Fall Example • Jason hits a volleyball with an initial velocity of 6.0 m/s upward. If the ball starts 2 m above the floor, how long will it be in the air?

  30. Assignment • Page 64 1-4 • a) -42 m/s b) 11 s • a) 22.1 m/s b) 2.25 s • a) 8.0 m/s b) 1.63 s • 1.8 m

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