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Acceleration

Acceleration. Chapter 7. Left: 25 th June, 1992 . Mission STS-50. Acceleration is the rate of change of velocity with respect to time, i.e. So, where a =acceleration, v =final velocity, u =initial velocity, and t =time.

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Acceleration

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  1. Acceleration Chapter 7

  2. Left: 25th June,1992. Mission STS-50.

  3. Acceleration is the rate of change of velocity with respect to time, i.e. • So, • where a=acceleration, v=final velocity, u=initial velocity, and t=time. • The unit of acceleration is the metre per second squared (ms-2 or m/s/s).

  4. The three equations of motion for an object moving at constant acceleration in a straight line are: where s = displacement and the rest are as before.

  5. Proof of the above 3 equations: • To prove: v = u + a t From the definition of acceleration we have,

  6. To prove: When the acceleration is constant, the average velocity is given by: • So, rewriting we have,

  7. To prove: Squaring both sides of v = u + at gives v2 =(u + at)2 But • Sowe have,

  8. Velocity-Time Graphs • Consider a car moving with a rightward (+), changing velocity – that is, a car that is moving rightward and speeding up or accelerating. Since the car is moving in the positive direction and speeding up, it is said to have a positive acceleration.

  9. If the velocity-time data for such a car were graphed, the resulting graph would look like the previous graph. Note that a motion with changing, positive velocity results in a diagonal line when plotted as a velocity-time graph. The slope of this line is positive, corresponding to the positive acceleration. In addition, only positive velocity values are plotted, corresponding to a motion with positive velocity.

  10. We know time, initial speed, final speed. Find the acceleration & distance Also find deceleration! We know time, final speed, initial speed Find acceleration & distance Using the Equations of motion… Click on pics

  11. Acceleration due to gravity

  12. Galileo’s Experiment

  13. Elephant and Feather But with air resistance

  14. The Galileo of Lemmings…

  15. If you drop an object, the force of gravity causes it to accelerate downwards this is due to the weight of the object. • With no air resistance, all objects near the earth’s surface, if released will fall downwards with the same acceleration. • This acceleration is called the acceleration due to gravity, its symbol is ‘g’ and at sea level it has a value of 9.8m s-2. • The value of ‘g’ decreases as you move away from the centre of the earth. So you’d weigh less on the top of Mt. Everest (g=9.77m s-2) than you would at sea level (g=9.81m s-2)!

  16. Standing next to the edge of a cliff, a person fires two shots from a gun, one (a) straight upward, the other, (b) straight downward. The gun shoots pellets at 30m/s from the barrel. • Ignoring air resistance, in which scenario (a) or (b) does the pellet hit the ground at the bottom of the cliff with the greatest velocity?

  17. Climbers on southeast ridge, Everest.

  18. Bravia ad… How this ad was made…

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