7.2.P4
Although all energy is kinetic and potential* it is convenient to break it up into
- coherent macroscopic kinetic energy (KE),
- macroscopic potential energy (PE),
- thermal energy (ThE = kinetic and potential energy of molecules due to random motion),
- chemical energy (ChE = kinetic and potential energy of electrons in atoms in molecule).
Consider a small rocket placed on a pad containing an electrical igniter.The rocket is attached to a small packet of chemical explosive in its tail. The igniter lights a short fuse that ignites the chemical explosive shooting the rocket upward. It rises straight up about 50 feet, then falls to the ground where it bounces and comes to a stop.
Consider three times: t0 = just after the explosion has completed but the rocket has not risen much, t1 = the rocket is just at the top, and t2 = the rocket has fallen to the ground and come to a stop.
Identify what has happened to the various energies of the rocket (not including the explosive packet or fuse) from the beginning to the end of the time segments indicated. Put +, -, or 0 in each of the boxes to indicate the particular component of the rocket's energy had increased, decreased, or remained the same. Put U (for unknown) if there is not enough information to decide.
|
Δ(Kinetic energy) |
Δ(Potential Energy) |
Δ(Thermal Energy) |
Δ(Chemical Energy) |
t0 to t1 |
|
|
|
|
t1 to t2 |
|
|
|
|
Explain how you decided each of the changes.
Joe Redish 1/30/18
* Of course this does not conclude the energy contained in mass (E = mc2) that we have to include when we get to the physics of the atomic nucleus!
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