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Presentation On Motion

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Published in: Physics
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This Physics PPT is suitable for IGCSE and O level students. The practice questions, worksheets and topical questions will be discussed during tutoring sessions.

Tahzeeb I / Dubai

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Teaches: Advanced Maths, Basic Computer, Coding & Programming, Mathematics, Matlab, Physics, Engineering, Chemistry, Computer Science, Maths

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  1. Motion Physics (IGCSE / O Level)
  2. What will you learn in this lesson? Speed Velocity Acceleration / Deceleration Determine from the shapes of a distance—time graph when an object is: (a) at rest (b) moving with constant speed (c) accelerating (d) decelerating Determine from the shape of a speed—time graph when an object is: (a) at rest (b) moving with constant speed (c) moving with constant acceleration (d) moving with changing acceleration Determine the distance from speed-time graph Determine the speed and acceleration from gradients on distance-time and speed-time graphs respectively
  3. Speed The distance travelled by object per unit of time distance moved average speed — time taken Average speed does not show whether the speed was steady or changing throughout the distance Runners don't run at constant speed during the whole time. So the L average speed is found out to calculate the individual's speed
  4. Speed (contd.) The Sl unit for distance is meter, m and for time is second, s. What will be the unit of speed? Distance can be measured in m, km, feet, miles, nautical miles (A nautical mile is a unit of length used in air, marine, and space navigation). Time can be measured in sec, min and h The unit of speed will be changed according to the ratio of units of distance and time
  5. Speed (contd.) What is the average speed of A acarthattravels400m in 20s. b an. athletewho runs 1500m in 4minutes? Give your answer in km/h for part (a) and m/s for part (b)
  6. Speed (contd.) Rearranging the equation of speed to find distance and time Symbolic representation: distance = speed x time or s — or t =
  7. Distance-Time Graph speed = slope or gradient of distance-time graph Slope — — 10 m/s
  8. Distance-Time Graph (contd.) When the speed of the body is changing, the slope of the distance—time graph varies and at any point equals the slope of the tangent. For example, the slope of the tangent at T is AB/BC = 40 m/2 s = 20 m/s. The velocity at the instant corresponding to T is therefore 20 m/s. 10 o 1 c 2 3 4
  9. Distance-Time Graph (contd.) Which part(s) of the graph shows non- uniform speed? ÆTURNING START Which part(s) of the graph shows the vehicle is slowing down (decelerating)? Which part(s) of the red graph shows the vehicle is speeding up (accelerating)? Which part(s) of the graph has the highest speed or fastest? TIME
  10. Velocity In physics, speed and velocity have different meanings. Velocity is a vector quantity. It has both magnitude and direction. It is the distance travelled in unit time in a stated direction. Speed is a scalar quantity. It has magnitude only. 300 km/h Velocity: 300 (El .3@km/h Speed is same but velocity is different due to change in direction
  11. Acceleration Acceleration is the change in velocity (how much it speeds up) over the time taken(how long it takes to speed up) If a body is moving with uniform acceleration a and its velocity increases from u to v in time t, then Note that the initial velocity u and the final velocity v refer to the start and the finish of the timing and do not necessarily mean the start and finish of the motion
  12. Acceleration (contd.) Unit for acceleration is m/s2, if the change of velocity is in m/s and time taken for the change is in seconds. 2 m/s2 can be represented as acceleration of 2 m/s in 1 s Acceleration can be negative if the final velocity is lower than initial velocity. This is called as deceleration.
  13. Speed-Time Graph acceleration = slope or gradient of speed-time graph A horizontal graph (slope means a constant speed me The steeper the slope the greater the acceleration, increasing speed A negative slo means a deceleration, Decreasing speed A horizontal graph (slope along time axis means speed has decreased to zero and the body is stationary
  14. Speed-Time Graph (contd.) What will be the acceleration when the graph is horizontal (or slope = O)? These curved lines shows the change in acceleration when change of speed is not steady c The The straight line show the speed is changed at steady rate
  15. Speed-Time Graph (contd.) Find the acceleration using gradient method 20 25
  16. Speed-Time Graph (contd.) Acceleration at any point in a non-uniform speed-time graph can be found using tangent and then find the gradient Tangent, to find acceleration at 5.5 seconds 40 -a 30 100 Time/ s 10 Time / s 15 What will be the acceleration at 5.5 seconds?
  17. Speed-Time Graph (contd.) Distance = area under the speed-time graph The area under the speed-time graph can be made up of rectangles and triangles area of rectanøe — Width * height area of a triangle * base height shaded ar•a — tr•velled 10 Which graphs show the uniform acceleration and zero acceleration? The unit of time must be same for both the axes
  18. Speed-Time Graph (contd.) A train's motion is represented by the following graph. Calculate the distance the train travelled in 60 sec. 140 60 Time / s