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CfE Higher Physics

CfE Higher Physics. Unit 1 Our Dynamic Universe Velocity-Time Graphs. Learning Intentions. Can I interpret velocity–time graphs including : a ) area under graph is displacement b ) gradient is acceleration

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CfE Higher Physics

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  1. CfE Higher Physics Unit 1 Our Dynamic Universe Velocity-Time Graphs

  2. Learning Intentions • Can I interpret velocity–time graphs including: a) area under graph is displacement b) gradient is acceleration c) objects in freefall taking into account air resistance and changing surface area. d) change a v-t graph into an a-t graph.

  3. Velocity-time graphs • From N5, you will already know the following: • The area under these graphs will be the displacement of the object. • The acceleration of the object can be found by finding the gradient of the lines.

  4. A B velocity C O time Velocity-Time Graphs OA - constant acceleration AB - constant velocity BC - constant deceleration acceleration = gradient of graph displacement travelled = area under graph

  5. Velocity-time graphs • As we have previously learned, the direction of the object will tell us if it has a positive or negative value. • Remember that UPWARDS is positive and DOWNWARDS is negative. • Gravity always acts down. • The following graph will show these.

  6. A B + C F time velocity O - E D Velocity-Time Graphs – directions Positive direction Negative direction OA - constant acceleration CD - constant acceleration AB - constant velocity DE - constant velocity BC - constant deceleration EF - constant deceleration

  7. Velocity-time graphs for objects travelling vertically • When a ball is thrown up vertically, we take the following vectors as positive: • Displacement • Velocity The acceleration due to gravity still acts downwards. What would you expect the graph to look like?

  8. Ball Thrown upwards

  9. Ball Thrown upwards and coming back down At the highest point, you can see that the final speed is 0 m/s https://www.youtube.com/watch?v=3jfoJpIYzXU

  10. Ball thrown up, comes down and hits the ground. Always split the journey into UP and DOWN. As it travels downwards, the final speed now becomes the initial speed. i.e. u = 0 m/s

  11. Some reminders • For all of these examples, air resistance is negligible. • Acceleration due to gravity is – 9.8 m s-2 • At the highest height of travel, the final velocity is ZERO m/s. • Velocity and Displacement are positive upwards • Velocity and Displacement are negative downwards

  12. The bouncing Ball • For an object that is dropped and bounces, what would you expect the velocity- time graph to look like? https://www.youtube.com/watch?v=t511816eZf4

  13. Acceleration-time graphs • What would the following velocity – time graph look like as an acceleration – time graph?

  14. A B + + C F B D C time velocity time acceleration O O A E F - - E D v-t Graphs into a-t graphs

  15. + B D C time acceleration O A E F - Acceleration-Time Graphs

  16. Success Criteria • I can interpret velocity–time graphs including: • a) area under graph is displacement • b) gradient is acceleration • c) objects in freefall taking into account air resistance and changing surface area. • d) change a v-t graph into an a-t graph.

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