Work and Energy — Important Questions

Lifting a book from floor to table, Pushing a moving cart, Pulling a trolley that moves forward

Work is done when force acts and object moves. Lifting a book (force upward, book moves up), pushing a moving cart (force applied, cart moves), and pulling a trolley (force applied, trolley moves) all satisfy both conditions. Holding a bag stationary and studying involve no displacement.

Kinetic energy

Kinetic energy is the energy possessed by an object due to its motion. Moving objects like a running car, flying bird, or flowing water have kinetic energy. Potential energy is due to position, heat and chemical energy are other forms.

Mass of the object, Velocity of the object

From the formula KE = ½mv², kinetic energy depends on mass (m) and velocity (v) of the object. It increases with both mass and velocity. Height affects potential energy, while color and temperature don't affect kinetic energy.

Four times

Since KE = ½mv², when velocity is doubled, KE = ½m(2v)² = ½m(4v²) = 4(½mv²). The kinetic energy becomes 4 times the original value because velocity is squared in the formula.