Question

if you push a heavy box which is rest, you must exert some force to start its motion. However once the box is sliding you apply a lesser force to maintain that motion. why? ​

Answer 1

Heavy box which is at rest posses Static friction. And sliding box posses sliding friction. Static friction>sliding friction>rolling friction. Therefore in order to move a bo at rest we have to overcome static friction and we have ro apply more force.