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Speed, Velocity, Acceleration

Speed, Velocity, Acceleration. BY: BRIANNA SHIELDS. DO NOW- Get hmwk out!. Complete the physics handout on front counter. GOAL. To interpret graphs and solve word problems involving speed, velocity, acceleration and momentum. Motion. Change in position during a time period

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Speed, Velocity, Acceleration

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  1. Speed, Velocity, Acceleration BY: BRIANNA SHIELDS

  2. DO NOW- Get hmwk out! • Complete the physics handout on front counter

  3. GOAL • To interpret graphs and solve word problems involving speed, velocity, acceleration and momentum

  4. Motion Change in position during a time period 3 types of motion Speed Velocity Acceleration

  5. Speed 1. Definition: Rate at which an object moves 2. Formula: Distance divided by time (d/t) 3. Units: m/s or km/s

  6. Speed 4. Constant speed - speed that doesn’t change 5. Average speed- add speeds, divide by total number

  7. Speed: Average vs. Instantaneous

  8. Speed 6. Graphs: Time: x-axis Distance: y-axis Constant speed Changing speed Copy samples of these into your notebook

  9. Cheetah Speed Graph • In one second how far had the cheetah run? • In three seconds how far had the cheetah run? • What was the cheetah’s average speed?

  10. Bicycle Graph • After one hour how far had she traveled? • Two hours? • Three hours? • Four hours? • Is she traveling at a constant speed? Why/why not • During which hours was her speed the greatest? • What does the flat line on the graph indicate?

  11. Distance vs. Time

  12. Calculating Speed: Example • If 2 runners ran the same distance (10km) but one completed it in 3600 seconds and the other in 2800 seconds, what were each of their average speeds? • 1: d/t 10km/3600 sec .00278 km/sec • 2: d/t 10 km/ 2800 sec .00357 km/sec • Runner 2 has greatest average speed!

  13. Calculating Speed: Example • Spirit of Australia, a hydroplane boat, made speed records by traveling 239 miles in 0.75 hours (45 minutes). What is it’s record breaking speed? • d/t 239 miles/ 0.75 hr

  14. Velocity 1. Definition: Describes speed plus direction (n, s, e, w) 2. Formula: D/T plus direction 3. Units: m/s or km/s, north, south, east or west

  15. Velocity 4. Velocities can be combined Add velocities when in same direction Velocities in opposite direction= subtract

  16. Velocity 5. Graphs: Time: x-axis Distance: y-axis (same as speed graphs but also has direction)

  17. Calculating Velocity: Example • If a runner is running east at 10 m/s sec, what is her velocity? • 10 m/s east

  18. Calculating Velocity: Example • If you’re rowing a boat downstream at 16 km/hr, and the curren is moving at 10 km/hr. How fast does the boat “look” like it’s going to someone on shore? (Draw a picture too!) • 16 + 10 • 26 km/hr downstream

  19. Calculating Velocity: Example • If you’re rowing a boat upstream at 15 km/hr, against a current moving at 8 km/hr. What is you’re actual velocity to an observer on the shore? • 15-8 • 7 km/hr upstream

  20. Calculating Velocity: Example • If you are running up an escalator at 2 steps per second and its moving downward at 3 steps per second, what is the total velocity? In what way are you moving? • 3-2 • -1 (you are actually moving backwards, down the escalator, although you’re running up it)

  21. Acceleration 1. Definition: Rate of change in velocity Speeding up, slowing down, changing direction 2. Formula: Final velocity minus original velocity, divided by time 3. Units: m/s/s or km/s/s

  22. Acceleration 4. Increasing velocity - positive acceleration 5. Decreasing velocity - negative acceleration- deceleration

  23. Acceleration 6. Graphs X- axis- time Y-axis- distance Object must be changing velocity Line, is smooth and curved (not straight)- “changing line”

  24. Acceleration Graph- Race Car • 1. From 0-1 sec how far did the race car go? • 2. From 1-2 sec? • 3. From 2-3 sec? • 4. Is the car accelerating or decelerating? Explain.

  25. Velocity vs. Time

  26. Comparing velocity and acceleration

  27. Calculating Acceleration: Example • A roller coaster’s velocity at the top of a hill is 10m/s. Two sec later it reaches the bottom of the hill with a velocity of 26 m/s. What is the acceleration of the roller coaster? • Vf-Vo T 26-10 2 8 m/s/s

  28. Calculating Acceleration: Example • A roller coaster’s velocity at the bottom of a hill is 25 m/s. Three seconds later it reaches the top of the next hill, moving at 10 m/s. What is the deceleration of the roller coaster? • A = Vf-Vo T A = 10-25 = -7.5 m/s/s 2

  29. Calculating Acceleration: Example • A car is traveling at 60 km/hr. It accelerates to 85 km/hr in 5 seconds. What is the acceleration of the car? • A = Vf-Vo T A = 85-60 = 5.0 m/s/s 5

  30. Momentum 1. Definition: Depends on object’s mass and velocity Related to force upon impact 2. Formula: Mass x velocity 3. Units: Kg.m/s

  31. Momentum

  32. Momentum

  33. Momentum

  34. Calculating Momentum: Examples • If 2 football players are running at the same velocity towards an opponent. Player 1 weighed 170 lbs, player 2 weighed 250 lbs. Who is going to move the opponent farther? Why? • Since both players were traveling at the same velocity, the larger player will have more momentum, thus, moving the opponent farther

  35. Calculating Momentum: Examples • Why would it be harder to stop a car traveling at 65 miles/ hr than it is to stop one traveling at 35 miles/hr? Explain • If they have approximately the same mass, the faster car will gather more momentum, according to the equation: momentum = mass x velocity

  36. Calculating Momentum: Examples • What is the momentum of a 0.3 kg bluejay running into a window while flying at 17 m/s? • momentum = mass x velocity • = 0.3 x 17 = 5.1 kg m/s

  37. Websites • Fear of Physics

  38. Assignment • Write the homework assignment into your agenda: • Practicing Motion

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