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Following a rocket

Page history last edited by Joe Redish 6 years, 1 month ago

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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