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ENERGY

ENERGY. Energy. Is transferred within a SYSTEM of objects Isn’t a “thing”. Analogy: Wealth. E g -- Gravitational Potential Energy energy due to an object’s change in height above earth (or other celestial body). Evidence : Δ height above h = 0. h = 0 meters.

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ENERGY

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  1. ENERGY

  2. Energy • Is transferred within a SYSTEM of objects • Isn’t a “thing”. Analogy: Wealth

  3. Eg -- Gravitational Potential Energy energy due to an object’s change in height above earth (or other celestial body) Evidence : Δheight above h = 0 h = 0 meters System: an object and the earth (or other large object). Eg is impossible with one object alone.

  4. Evidence: food batteries fuel Echem --Chemical Potential Energy energy transferred in chemical reactions (transfer of electrons)

  5. Eel -- Elastic Potential Energy energy stored in a spring or other elastic object Evidence : object is de-formed (and it can re-form)

  6. Ek -- Kinetic Energy Evidence: velocity (motion)

  7. Edis -- Dissipated Energy ---- Energy transferred to the surrounding environment. Evidence: light, heat, sound; friction

  8. Summary How we know • Eg • Ek • Echem • Eel • Edis

  9. Other Energy we won’t be discussing right away Mass energy E = mc2 Converted by nuclear reactions

  10. Electric Energy Other Energy we won’t be discussing right away (or at all) • Stored in an electric field -- due to + and – charges separated from each other Magnetic Energy • Stored in a magnetic field - due to North and South poles of a magnet separated from each other, (or from moving charges)

  11. Q: How do we show Energy Transfersbetween objects? Answer: Energy Bar Charts • Show Energy distribution at 2 or more instants in time

  12. Examples of Bar Charts to show Conservation of Energy within a system • 2010 olympics - aerial skiing (start at 00:43 sec)

  13. Top (before jump) On ramp Eg Ek Edis Eg stopped In air Edis Eg Ek Edis Aerial skiing Energy is always dissipated to other objects in the system as time goes on

  14. worlds tallest bungee jump - start at 1:40

  15. In air Top (before jump) Ek Edis Eg Eg During stretch of elastic stopped Edis Ek Edis EEl Eg Bungee Jump

  16. What is this story? Ek Ek Eg Edis Eg Edis

  17. v (m/s) X (m) a (m/s2) t(s) ΣF (N) ΣF (N) Ff (N) Fg = weight (N) t (S) Mass (kg) FN (N) a (m/s2) What is the physical meaning of each SLOPE and AREA? Avg. Velocity Slope: Acceleration jerk t(s) t(s) Displacement = Δx meaningless Δv Area: Gravitational Field Strength (N/kg) Mass (N/m/s/s = kg) μ meaningless Slope: Impulse meaningless meaningless meaningless Area:

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