Gravity

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gravity slideshow by idrul nafiz

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Gravity

  1. 2. <ul><li>What is acceleration? </li></ul><ul><li>What is mass? </li></ul><ul><li>What is force? </li></ul>
  2. 3. <ul><li>When the ball is release, the ball will reach the ground. Why? </li></ul>
  3. 4. <ul><li>2.8 Understanding Gravity </li></ul>
  4. 5. <ul><li>Explain and determine the value of acceleration due to gravity </li></ul><ul><li>Define gravitational field and gravitational strength </li></ul><ul><li>Define weight </li></ul><ul><li>Solve problems involving acceleration due to gravity </li></ul>
  5. 6. <ul><li>To study the relationship between acceleration of an object and mass </li></ul><ul><li>Material : </li></ul><ul><li>Water bottle (2) </li></ul>
  6. 7. <ul><li>Conclusion </li></ul>Both objects reach the bottom at the same time The acceleration of an objects does not depend on the mass
  7. 8. <ul><li>Definition: Acceleration of an object due to the pull of the gravitational force only. </li></ul><ul><li>The value of acceleration due to gravity, g is </li></ul><ul><li> 9.8 ms -2 </li></ul><ul><li>An object is falls freely under the influence of gravitational force only </li></ul>
  8. 11. <ul><li>Definition: Region in which an object experiences a force due to gravitational attraction </li></ul><ul><li>Any massive object that enters this field will experience a force of attraction </li></ul><ul><li>This field will get weaker the further you go out from the centre of earth </li></ul>
  9. 12. Earth: half size Earth: Half Size GRAVITATIONAL FIELD
  10. 13. <ul><li>Gravitational field strength is defined as the gravitational force per unit mass </li></ul><ul><li>Gravitational field strength of the earth is 9.8 N kg -1 </li></ul><ul><li>Gravitational field strength of moon is </li></ul><ul><li>1.6 N kg -1 </li></ul>
  11. 14. <ul><li>A ball falls vertically a distance of 125 m to the ground. Using g = 9.8 ms -2 ; calculate: </li></ul><ul><li>Time the ball takes to fall the first 25m </li></ul><ul><li>Time the ball takes to reach the ground </li></ul><ul><li>The velocity of ball before it hits the ground </li></ul>
  12. 15. <ul><li>Define: Gravitational force acting on a body </li></ul><ul><li>Where mass is m and g is gravitational field strength or the acceleration due to gravity </li></ul><ul><li>Unit = N </li></ul>
  13. 16. <ul><li>What is Ali’s weight on the earth and moon if its mass is 70kg? </li></ul><ul><li>Use g earth = 9.8 ms -2 and g moon = 1.6 ms -2 </li></ul>
  14. 17. <ul><li>Question time… </li></ul><ul><li>1 2 </li></ul><ul><li>3 4 </li></ul>
  15. 18. <ul><li>Question 1 </li></ul><ul><li>Our bodies are pulled down to the earth's surface by </li></ul><ul><li>Newton’s </li></ul><ul><li>Weight </li></ul><ul><li>Gravity </li></ul>
  16. 19. <ul><li>Question 2 </li></ul><ul><li>Object with different mass have ……… acceleration due to gravity </li></ul><ul><li>Difference </li></ul><ul><li>Same </li></ul><ul><li>Zero </li></ul>
  17. 20. <ul><li>Question 3 </li></ul><ul><li>Value of acceleration due to gravity on earth is 9.8 ms -1 </li></ul><ul><li>True </li></ul><ul><li>False </li></ul>
  18. 21. <ul><li>Question 4 </li></ul><ul><li>If an object fall with an acceleration due to gravity, the velocity of the object must…… </li></ul><ul><li>Be constant </li></ul><ul><li>Continuously change by the same amount each second </li></ul><ul><li>Continuously change by varying amount each second </li></ul><ul><li>Continuously decrease </li></ul>
  19. 22. <ul><li>Acceleration due to gravity is the acceleration of an object due to the pull of the gravitational force </li></ul><ul><li>Gravitational field is the region in which an object experiences a force due to gravitational attraction </li></ul><ul><li>Free fall is an object falls under the influence of gravitational force only </li></ul><ul><li>Gravitational field strength is the gravitational force per unit mass </li></ul><ul><li>Weight is the gravitational force acting on a body </li></ul>

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