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Velocity & Acceleration

Learn about velocity, speed, acceleration, and their formulas. Understand how to calculate them with examples and grasp their significance in physics.

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Velocity & Acceleration

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  1. Velocity & Acceleration Some Review

  2. Defining Velocity Kinetic energy was • KE=1/2 (mass) (velocity)2 We know that the mass of an object is the actual amount of matter in the object expressed in grams or kilograms.

  3. Velocity • Describes both the rate and direction of the motion • If an object speeds up or slows down in the given direction we say there is a change in velocity

  4. VELOCITY AND SPEED Velocity is a measure of how fast an object is traveling in a particular direction. OR The rate of change of an object’s position • Velocity changes as speed or direction changes • Is constant only if both its speed and direction remain the same Bus traveling 15 m/s south increases speed to 10 m/s south – speed changed – so did velocity

  5. VELOCITY Velocity = distance ÷ time The units we use are m/s and d is distance. Rearranging the formulas for all possibilities: V= d/t d = vt t = d/v

  6. VELOCITY • What is the velocity of a car that travels 100m north in 2 hours? V = d/t 100.m/2h = 50.0m/h A car travels 65.0m/h east for 3.00 hours how far did it go? d = vt (65.0m/h) (3.00h) = 195m = How long would it take a car to travel 200 miles south at a velocity of 70m/h? t = d/v t = 200m/70m/h t = 2.9h = 3hr Make sure you work your problems so that units cancel out.

  7. Speed Speed = Distance x Time • distance an object moves per time • measure of how fast an object is moving • Does not include a direction • Merry-go-round – does not move in a single direction so does not have velocity

  8. ACCELERATION • Acceleration is the change in velocity per unit of time. • An example of this is when you travel in your car. • Your velocity is not constant throughout the entire trip as you slow down and speed up as necessary. • A positive acceleration means that you are speeding up and a negative acceleration means that you are slowing down.

  9. ACCELERATION • Acceleration has the formula: Acceleration = (Final Velocity) – (initial velocity) (Final time) – (Initial time) OR (time it takes to change velocity) A = vf – vi = ∆v ∆ means “change in” tf – ti ∆ t Acceleration has the units of (distance unit)/(time unit) Ex: m/s2 or mi/h2

  10. ACCELERATION • Example acceleration problems • Calculate the acceleration of an object with: • Initial Velocity : 0.0m/s • Final Velocity: 14m/s • Time 4.0s • A = 14m/s – 0.0 m/s 4.0s A = 3.5m/s2

  11. ACCELERATION • A car stops from a velocity of 55m/s in 15 seconds. What is the cars acceleration? Is the car speeding up or slowing down? • A = 0 – 55m/s = -55m/s 15 s 15s A = -3.7m/s2 Car is slowing down

  12. ACCELERATION • A runner achieves a velocity of 21.1m/s 10.0 seconds after he begins. What is his acceleration? What distance did he cover in the 10.0 seconds? • a = 21.1m/s – 0 a = 2.11m/s2 10.0s d = v t (21.1m/s)(10.0s)= 211m

  13. Examples of Acceleration

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