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Acceleration

Acceleration. and Gravity. Acceleration The rate at which velocity changes. Includes: increasing speed decreasing speed changing direction (with no change in velocity). How do you find the acceleration?. final velocity – initial velocity time. acceleration =.

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Acceleration

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  1. Acceleration and Gravity

  2. Acceleration • The rate at which velocity changes. • Includes: • increasing speed • decreasing speed • changing direction (with no • change in velocity)

  3. How do you find the acceleration? final velocity – initial velocity time acceleration = *If answer is positive -> speeding up *If answer is negative -> slowing down *Units are m/s or m/s² s

  4. Sample problem 1: A car traveling east accelerates from 10m/s to 73m/s in 9.0 seconds. Calculate its acceleration. Step 1: list the variables -> vi = 10 m/s -> vf = 73 m/s -> t = 9.0 s Step 2: Substitute a = vf – vi = 73m/s – 10m/s t 9.0s Step 3: Solve a = 63m/s = 7m/s2 9.0s

  5. Gravity • force that pulls objects toward each other • Law of Universal Gravitation – the force of gravity acts between all objects in the universe. • Mass and distance affect the gravitational attraction between two objects.

  6. Mass and Weight • Mass – a measure of the amount of matter in an object • measured in grams, kilograms, pounds, etc. • mass of an object does not change • Weight – the force of gravity on a person or object at the surface of a planet. • measured in Newtons (N) • weight of an object can change • weight = mass x gravity An astronaut in a spacesuit… Mass on Earth -> 165 kg Weight on Earth -> 1617 N Mass on the moon -> 165 kg Weight on the moon -> 270 N

  7. Sample problem 2: If a person has a mass of 132pounds, what is their weight? Step 1: Convert to metric units if needed. 2.2 lbs = 1 kg 132lbs ÷ 2.2 lbs/kg = 60kg Step 2: Substitute W = m x g W = 60kg x 9.8 m/s2 Step 3: Solve W = 588 N

  8. Acceleration Due to Gravity • When gravity is the main force acting on an • object, the object will accelerate. • On Earth, the acceleration due to gravity is • 9.8 m/s2 • This means that it would increase 9.8m/s2 • for each second it falls… • 1 second -> 9.8m/s2 • 2 seconds -> 19.6m/s2 • 3 seconds -> 29.4m/s2

  9. Acceleration due to gravity continued… • Air resistance opposes acceleration due to gravity. • The greater the surface area, the greater the air resistance that acts on it. • Terminal velocity - velocity at which the force of air resistance equals the weight of the object. (Forces are balanced, so no acceleration, but velocity remains constant.) • In the absence of air, all things will truly fall with the same acceleration. Feather and hammer on the moon

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