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BR: What is Kinetic Energy?

BR: What is Kinetic Energy?. Kinetic Energy. Energy in motion. Standards HW. H.P.3 The student will demonstrate an understanding of how the interactions among objects can be explained and predicted using the concept of the conservation of energy.

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BR: What is Kinetic Energy?

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  1. BR: What is Kinetic Energy?

  2. Kinetic Energy • Energy in motion.

  3. Standards HW • H.P.3 The student will demonstrate an understanding of how the interactions among objects can be explained and predicted using the concept of the conservation of energy. • Review Kinetic and Potential Energy Problems • Remember to show all work when working problems PS-6.1 law of conservation of energy, 6.2 factors affecting potential/kinetic energy; PS-2.6 fission and fusion and PS-2.7 consequences of nuclear applications

  4. Kinetic Energy KE • KE = ½ mass x velocity OR KE = ½ m v 2 2

  5. Which has the most KE? • Which has the least KE? 80 km/h 50 km/h 80 km/h Energy • Kinetic Energy (KE) • energy in the form of motion • depends on mass and velocity 80 km/h truck 50 km/h motorcycle

  6. Watch me do a KE problem: • What is the kinetic energy of a 44kg cheetah running at 31 m/s? Given:Plan: 44 kg = m 31 m/s = v Find: ? = KE KE = ½ m v2 2 KE = ½ (44) x (31) KE = 22 x 961 KE = 21142 J

  7. Note: Kinetic energy depends more on speed than on mass.

  8. Mechanical Energy • The sum of the Potential and Kinetic energy in a system. * The total energy in the system

  9. Law of Conservation of Energy • Energy cannot be created nor destroyed it can only be changed. • Energy can be transferred to another object/system or to another form (like potential to kinetic)

  10. RECALL:Unstable Atoms and Energy

  11. Update Checklist • Types of energy • PE Calculations (how to) • KE Calculations (how to) • Unstable atoms and energy

  12. Let’s Quantify! Complete worksheet – Use your SEPs – show all math work ! Those who need extra help, meet in Plenary Session up front for more practice.

  13. Today in PSci, I • Examined the relationship between work and energy • Used math calculations to support the energy-work relationship in various situations

  14. Let’s talk it through… • KE = ½ m x v2 GPE = m x g x h • A cheetah can run briefly with a speed of 31 m/s. Suppose a cheetah with a mass of 47 kg runs at this speed. What is the cheetah’s kinetic energy? KE = 22583.5 J or 2.3 x 104 J • KE or GPE and how do you know? Which value is squared? Yes, the speed. The unit of speed is… m/s 31 m/s, Now finish the problem.

  15. KE = ½ m x v2 GPE = m x g x h • What is the gravitational potential energy associated with a 75 kg tourist at the top floor of the Sears Tower in Chicago, with respect to the street 436 m below? • A table tennis ball has a mass of about 2.45 g. Suppose the ball is hit across the table with a speed of 4.0 m/s. What is the ball’s kinetic energy?

  16. KE = ½ m x v2 GPE = m x g x h • An Olympic diver weighing 650 N is on a platform 10 m above the water. What is the diver’s gravitational potential energy with respect to the water? (Hint: m x g = weight in N or Fg) • A meteoroid entering Earth’s atmosphere has a speed of 70.0 km/s and a kinetic energy of 2.56 x 1015 J. What is the mass of the meteoroid?

  17. KE = ½ m x v2 GPE = m x g x h • The kinetic energy of a golf ball is measured to be 143 J. If the golf ball has a mass of 47g. what is its speed? (Hint: rearrange the equation for kinetic energy to solve for v. the equation will involve a square root)

  18. KE = ½ m x v2 GPE = m x g x h • A bird carries a 25 g oyster to a height of 11 m. What is the gravitational potential energy of the oyster? • The bird from problem 10 drops the oyster. As it falls, all of the gravitational potential energy is transformed into kinetic energy (air resistance is negligible). What is the speed of the oyster when it hits the ground?

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