As energy and work both are measured in joules. If we define work it is the force applied on an object as it moves a certain distance and Energy is the ability to do work. Both are closely related because work done on an object can cause a change in energy. Now if a ball is rolling down a hill then there is no frictional loss then its energy will be conserved but the work done by the ball will continuously change.Therefore they will both be measured in joules.
Velocity is a measure of both speed and direction of motion. Velocity is a vector, which is a measurement that includes both size and direction. Velocity can be represented by an arrow, with the length of the arrow representing speed and the way the arrow points representing direction.
