Motion Objectives Displacement velocity acceleration Motion with Constant
Motion Objectives: • Displacement, velocity, acceleration • Motion with Constant Acceleration • Free Fall
Distance and Displacement Q 1. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall, what is the total: Distance Displacement
Distance and Displacement Q 1. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall, what is the total: Distance: 7 m Displacement: 7 m Q 2. Now, you walk back to the wall where you started originally. What is the total: Distance: Displacement:
Distance and Displacement Distance Displacement The length of the path traveled The CHANGE in the position
Distance and Displacement Distance The length of the path traveled Displacement The CHANGE in the position Q 3. You dive in the swimming pool and begin to do laps. The swimming pool is 25 m long. After 2 complete laps, what is the distance traveled? (a) 0 (b) 50 (c) 100 (d) Cannot tell
Distance and Displacement Distance The length of the path traveled Displacement The CHANGE in the position Q 3. You dive in the swimming pool and begin to do laps. The swimming pool is 25 m long. After 2 complete laps, what is the distance traveled? (a) 0 (b) 50 (c) 100 (d) Cannot tell Q 4. What is your total displacement? (a) 0 (b) 50 (c) 100 (d) Cannot tell
Velocity and Speed speed = number distance traveled time it took velocity = number displacement change in position time it took + direction
Velocity and Speed speed = distance traveled time it took number velocity = number Speed or velocity? You are driving your car at 65 mph. You are lost and call a friend to tell him you are driving north at 45 mph You tune in to the Weather channel and they report north-west winds at 50 mph displacement change in position time it took + direction
Velocity and Speed speed = number distance traveled time it took velocity = number displacement change in position time it took + direction Q 5. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall and back in 10 s. What was your speed? And your velocity?
Velocity and Speed speed distance traveled = time it took number velocity = number displacement change in position time it took + direction Q 5. The width of a room is 7 m (approx. 7 yards). You walk from one wall to the other wall and back in 10 s. What was your speed? And your velocity? speed = distance traveled time it took ? velocity displacement = = time it took ?
Acceleration average speed = distance traveled time it took average velocity = average acceleration = displacement change in position time it took change in velocity time it took
Acceleration average speed = distance traveled time it took average velocity = average acceleration = displacement change in position time it took change in velocity time it took Q 6. Claims on the web state that a NASCAR Cup car can run 0 – 60 in 3. 0 s. What is its average acceleration? ? average acceleration = change in velocity Ans. time it took ?
Displacement, Velocity, Acceleration 20 P 1. Your speedometer reads 50 mph. Is this average speed or instantaneous? Answer: P 2. You are driving at 35 mph. What Is that in m/s? Answer: P 3. A car accelerates from 60 ft/s to 70 ft/s. What Is its average acceleration? What is the acceleration in m/s? Answer: P 4. A pick up truck pulling a trailer accelerates at 3. 25 m/s 2 for 5. 80 s. If it starts from rest, what is its final velocity? Answer:
Average vs. Instantaneous Q 7. How can we calculate the speed or velocity at one instant? acceleration = constant velocity = Beginning velocity position = beginning position + acceleration x + beginning velocity time elapsed x time elapsed + 0. 5 acceleration x time elapsed 2
Free Fall Q 8. Which one will hit the ground first? (a) Ball (b) Paper (c) Both (d) Cannot tell
Free Fall Galileo (1589): 1 s: 186 ft 2 s: 3 s: 16 ft 64 ft 144 ft
Free Fall Galileo (1589): 1 s: 186 ft 2 s: 3 s: Pattern 16 ft 1 64 ft 4 144 ft 9 4 s: ? ? ft ? ?
Free Fall Apollo 15 Moon Experiment: 1 s: 2 s: 3 s: Apollo 15 Moon Experment with a Hammer and a Feather Pattern 16 ft 1 64 ft 4 144 ft 9
Free Fall: Example Q 9. The acceleration due to Earth’s Gravity is 9. 8 m/s 2. What is that in ft/s 2? Answer:
Free Fall: Example 10 min Q 10. If you drop a rock from the top of a building and it hits the ground 1. 5 s later, how tall is the building in ft? acceleration = 32. 152 ft /s 2 velocity = Beginning velocity position = beginning position + 32. 152 ft /s 2 + beginning velocity x time elapsed + (0. 5) 32. 152 ft /s 2 x time elapsed 2
Free Fall Problems DIY P 1. Your speedometer reads 50 mph. Is this average speed or instantaneous? Answer: P 2. You are driving at 35 mph. What Is that in m/s? Answer: P 3. A car accelerates from 60 ft/s to 70 ft/s. What Is its average acceleration? What is the acceleration in m/s? Answer: P 4. A pick up truck pulling a trailer accelerates at 3. 25 m/s 2 for 5. 80 s. If it starts from rest, what is its final velocity? Answer:
Constant Acceleration Problems DIY P 1. You drop a rock from a bridge. It hits the water in 3. 0 s. How far below is the surface of the water? Answer: position = + x 2 + (0. 5) 32. 152 ft /s 2 x P 2. What will be the speed of a rock 1. 5 seconds after it has been dropped? Answer: velocity = + 32. 152 ft /s 2 x
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