Question

Compare situations where momentum and mechanical energy can be used alone or together at the same time and where both are used together. Think of how real-world problems are different from those in a classroom.

Answer 1

1. Motion of a planet around a star in elliptical orbit encompasses both Mechanical energy conservation law as well as angular momentum conservation law . By using both laws, motion of planet around a star is predicted.
2. Roller coaster ride is an example where only mechanical energy could be considered constant if friction/ drag is neglected. In other words, sum of gravitational potential energy and kinetic energy at any point in motion is conserved and this law is to predict motion of roller coaster.
3. Collision of two cars in a straight line is good example of linear momentum conservation where damage occurs so mechanical energy is no conserved but only momentum is conserved which could be used to ascertain their motion.