Work, Energy and power — Important Questions

A moving car, A bullet fired from a gun, A rolling ball

Kinetic energy is possessed by objects in motion. A moving car, bullet fired from gun, and rolling ball all have kinetic energy. A book on shelf has potential energy due to height, and stretched rubber band has elastic potential energy.

True

Kinetic energy is the energy possessed by a body due to its motion, and its expression is derived from the work done by a retarding force in bringing a moving body to rest. This derivation gives K = ½mv², where m is mass and v is velocity, confirming the statement as true.

Kinetic energy, Potential energy

Mechanical energy consists of only two types: kinetic energy (due to motion) and potential energy (due to position or configuration). Heat, light, and chemical energy are other forms of energy.

When force opposes displacement

Work done is negative when force opposes displacement (θ = 180°). Examples include friction force and gravitational force on upward motion. When θ = 90°, work is zero, and when displacement is zero, work is also zero.