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Energy And Turning Effect

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Energy And Turning Effect

1. 1. Energy and Turning Effect<br />Physics Chapter 1 and 2<br />
2. 2. ENERGY<br />“Energy is the ability to do work or to produce a change.”<br />
3. 3. Forms of energy<br />Potential energy – stored energy<br />*Elastic potential energy (rubber bands, basketball, etc.)<br />Gravitational potential energy<br />*Chemical potential energy (food, fuels, etc.)<br />*Electrical potential energy (covered in Chap. 5 : Electricity)<br />Kinetic energy – movement energy<br />*Heat energy (covered in Secondary 1)<br />*Light energy (covered in Chap. 2 and 3 : Light and Colour)<br />*Sound energy<br />Those marked with * are not very important.<br />
4. 4. Gravitational Potential energy<br />Gravitational energy is the energy an object has was it is raised above the ground.<br />The amount of gravitational energy depends on mass and height.<br />The larger the mass, the greater the gravitational energy. <br />The higher the object, the greater the gravitational energy.<br />The formula for finding Gravitational P.E. (in J) = mgh (Mass in kg x 10 N (on Earth) x Height above ground)<br />
5. 5. Kinetic Potential energy<br />Kinetic potential energy is the energy found in a moving body.<br />The amount of kinetic energy depends on mass and speed.<br />The larger the mass, the greater the kinetic energy. <br />The faster the object moves, the greater the kinetic energy.<br />The formula for finding Kinetic P.E. (in J) = 1/2mv2 (1/2x Mass in kg x Speed (m/s) x Speed)<br />
6. 6. Principle of Conservation of Energy<br />Energy cannot be created or destroyed, but only converted from one form to another.<br />Examples of Energy changes: <br />Burning pile of wood<br />Chemical Potential energy -&gt; Heat energy + Light energy<br />Basketball drops from a height<br />Gravitational Potential energy -&gt; Kinetic energy<br />
7. 7. Explaining why a basketball&apos;s rebound height is less than the initial dropped height<br />When the ball rebounds, air resistance is present.<br />Kinetic energy is converted to sound and heat energy when the ball hits the ground.<br />Hence the rebound height is less than the initial dropped height.<br />
8. 8. TURNING EFFECT<br />
9. 9. Turning Effect and Moment<br />The tendency for a force to produce rotation.<br />A force is a push or a pull that tends to produce motion, stop motion or change an object’s shape or size.<br />This turning effect is called moments.<br />Moment is the product of the force applied and the perpendicular distance from the pivot to the line of action of force.<br />
10. 10. Principle of Moment<br />The sum of anticlockwise moments about a pivot is equal to the sum of clockwise moments about the same pivot when an object is in equilibrium.<br />Clockwise moments = Anti-clockwise moments<br />For the principle to work:<br />Object must be pivoted at one point.<br />A force must act on the object, but not at the pivot.<br />
11. 11. Formula of Moment<br />Moment (in N m) = Force (N) x Perpendicular Distance (m)<br />