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Kinematics 1-D Motion. Vocabulary of Motion. Distance Scalar quantity Displacement Vector quantity, Object’s change in position. 5 km. Distance traveled = 15 km Displacement = 5 km, East. 5 km. 5 km. Vocabulary of Motion. Speed Scalar Quantity - Change in distance over time .
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Vocabulary of Motion • Distance • Scalar quantity • Displacement • Vector quantity, Object’s change in position
5 km • Distance traveled = 15 km • Displacement = 5 km, East 5 km 5 km
Vocabulary of Motion • Speed • Scalar Quantity - Change in distance over time
Vocabulary of Motion • Velocity • Vector Quantity • Average Velocity = v = Change in Position = Δd Change in Time Δt
Vocabulary of Motion • Acceleration • Vector Quantity a = Change in Velocity = Δv Change in Time Δt • Positive a – speeding up • Negative a – slowing down
Motion Graphs • Position Vs. Time Position Position Time Time v = + constant Object is Stopped, v = 0
Position Vs. Time Position Time v = - constant
(Not constant velocity) Position Position Time Time Object is decreasing speed over time
Position Position Time Time Walks away. Stops, walks back towards start and keeps going past 0, -. Object is increasing speed over time
Position Time Constant speed, slowing down to a stop, then increasing speed
Slope? • The slope of a Position vs. Time graph is the objects Velocity! Slope = Δy = Δd = v Δx = Δt
Which graph best represents the motion of a block accelerating uniformly down an inclined plane?
Motion Graphs • Velocity vs. Time Velocity Velocity Time Time Velocity is constant Increasing at a constant rate, +
Time Velocity Velocity Time Velocity is decreasing, stops and increases in the other direction Velocity is decreasing at a constant rate, -
Slope? • The slope of a velocity vs. Time graph is its acceleration! Slope = Δy = Δv = a Δx = Δt
Mathematical Analysis • Finding Average Velocity v = vi + vf or Δd 2 Δt Note: vi = Initial Velocity vf = Final Velocity
Acceleration a = Δv or vf – vi Δt Δt
Problems • A car travels 650 m in 5.0 sec. What is its average velocity??
Problems • A car starting at rest accelerates at 2.0 m/s2 for 2.0 sec. What is its final velocity? • A car is traveling at 35 m/s. It then accelerates at a rate of 6.0 m/s2 for 10 sec. Find the final velocity of the car.
Additional Motion Equations • d = vit + 1/2at2 • vf2 = vi2 + 2ad
On Your Own • A car is traveling at 35 m/s. It then accelerates at a rate of 6.0 m/s2 for 10 sec. Find the final velocity of the car.
Free Fall • All bodies fall at the same rate of acceleration • The acceleration due to gravity near the Earth’s surface is 9.81 m/s2
What does that mean? • Every second an object falls, its speed is increasing by 9.81 m/s
t = 0 sec, v = 0 m/s t = 1 sec, v = 9.81 (10) m/s t = 2 sec, v = 19.62 (20) m/s t = 3 sec, v = 29.43 (30) m/s
Motion Graphs Position Velocity Time Time
Mathematical Analysis of Free Fall • a = g = 9.81 m/s2 • For an object being dropped, The initial velocity is ZERO. • Motion in the y-direction (vertical)
Problem . . . • A 100 kg object is dropped from 10 m. How long does it take to hit? • What is the final speed right before it hits the ground?