Question

For each of the following situations, identify which of mechanical energy, kinetic energy, and momentum is/are conserved. Your answer may contain anywhere from zero to all three of these options. (pt each; pt bonus for getting 5 or more correct; another point bonus for getting all 7 correct) (a) A rock slides down a frictionless ski jump ramp, flies off the ramp, bounces off a vertical spring, and then is about to land on the ground. (b) At a July 4 fireworks show, a firework is shot into the air. Consider as it is rising toward its peak. (e) Now consider as it explodes. (d) Finally consider as the fragments fall back to earth (e) At the LHC accelerator, two lead nuclei collide in an inelastic collision. (1) Also at the LHC, two protons collide in an elastic collision (g) A US Air Force pilot ejects from his F18 jet and safely descends to earth with the use of his parachute.

Answer 1

A. Mechanical energy is conserved.

Velocity would change as it lands on spring and the K.E gets converted into Potential enegry of spring. So, since the velocity is not constant, momentum is also not conserved.

B. Machanical energy is conserved.

K.E decreases as it goes up and P.E increases which is maximum at maximum height when velocity becomes zero.

C. Momentum is conseved.

chemical energy gets converted into K.E and is not conserved however momentum is always conserved.

D. Mechanical energy is conseved. Gravitational force acts on the body so its momentum will not be conserved.

E. Momentum is conserved but some of the energies are lost as heat and sound while collision so K.E is nor conserved and so does mechanical energy.

F. In elastic collision there is no loss of energy so, Kinetic enegy, mechanical energy and mometum all are conserved.

g. Parachute experiences airdrag so enegy is lost in air friction.  So, nothing of the given is said to conserved in a parashut jump.