Answer
See answers.
Work Step by Step
a. Energy is a scalar, so the math does not involve vectors, components, etc. When using energy principles to solve a problem, the path followed by the particle, or the time taken, is not important: only the initial and final energies need to be calculated. Forces that perpendicular to the motion do no work and therefore don’t enter the energy calculations.
b. Never. The energy equations come from Newton’s Laws, so, force equations can always be used to find the motion of an object. However, at times, the force equations are so complex that it is much preferable to use energy equations.
c. Force equations must be used if you need to find something about the directions of motion (e.g., velocity or displacement components). Force equations must also be used to find the time taken to complete the motion, or an acceleration.
d. See part c for the information that cannot be obtained when solving problems with an energy approach.
