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ENERGY

ENERGY. Y7/SCIENCE/2012-2013. ENERGY-WORK-POWER. Energy is the ability to do work or cause change. Work is transfer of energy. Power is the rate at which energy is transferred. Power = energy transferred time Power = work = force x distance

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ENERGY

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  1. ENERGY Y7/SCIENCE/2012-2013

  2. ENERGY-WORK-POWER • Energy is the ability to do work or cause change. • Work is transfer of energy. • Power is the rate at which energy is transferred. • Power = energy transferred time • Power = work = force x distance time time

  3. KINETIC ENERGY = ½ x MASS x VELOCITY2 EQUAL VELOCITY EQUAL MASS Golf ball: Mass = 0.5 Kg Velocity = 10 m/s Ek= ½ x 0.5 x 100 = 25 J Bowling ball: Mass = 3 Kg (6x greater) Velocity = 10 m/s Ek= ½ x 3 x 100 = 150 J(also 6x greater) Bowling ball: Mass = 3 Kg Velocity = 4 m/s Ek= ½ x 3 x 16 = 24 J Bowling ball: Mass = 3 Kg Velocity = 12 m/s (3x greater) Ek= ½ x 3 x 144 = 216 J (>6x greater) VELOCITY has a greater effect on an object’s kinetic energy than its mass.

  4. POTENTIAL ENERGY = WEIGHT X HEIGHT EQUAL HEIGHT EQUAL WEIGHT Skier 1: • Weight = 300 N • Height= 10 m • Ep= 300 N x 10 m = 3 KJ • Skier 2: • Weight = 600 N (twice greater) • Height = 10 m • Ep= 600 N x 10 m = 6 KJ (twice greater) • Skier 1: • Weight = 500 N • Height = 10 m • Ep= 500 N x 40 m = 5 KJ • Skier 2: • Weight = 500 N • Height = 20m (twice greater) • Ep= 500 N x 50 m = 10 KJ (twice greater) BOTH weight and height have the same effect on an object’s potential energy. When the weight or height is doubled, the potential energy is also doubled.

  5. YOUR TASK TODAY! • INDIVIDUAL WORK. • PLEASE COMPLETE SECTION 1 ASSESSMENT. • TEXTBOOK PAGE 150 NUMBER 1-4. • DO IT IN YOUR CAMPUS FILE. • DUE: TODAY AT THE END OF SCIENCE LESSON. • THANK YOU IN ADVANCE FOR DOING YOUR BEST!

  6. Section 1 Assessment p. 150 nr. 1 a. What is energy? Energy is the ability to do work or cause change. b. How are energy, work, and power related? When work is done on an object, energy is transferred to the object. The amount of energy transferred (or work done) in a unit of time is power. c. If they do the same amount of work, which has more power: a handsaw or a chainsaw? The chainsaw has more power because it transfers energy to the log faster than the handsaw.

  7. Section 1 Assessment p. 150 nr. 2 a. What is kinetic energy? Kinetic energy is the energy an object has due to its motion. (kinetic = kinetos (Greek) = moving) What is potential energy? Potential energy is the stored energy an object has due to its position or shape. b. What factors affect an object’s kinetic energy? mass and velocity c. How would you determine the potential energy and kinetic energy of a skydiver? Ep = weight x height = mass x gravity x height Ek = ½ x mass x velocity2

  8. Section 1 Assessment p. 150 nr. 3-4 3. What is the value of the number 102? 102 = 10 x 10 = 100 4. What number when squared gives you the value 36? …2 = 36  … = √36 = 6

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