Lifting the backpack off the floor. Force is being applied in only one direction then (up) which is what constitutes as work. Carrying the box of crayons applies force in two directions (up and forward), which cancel each other out. Work has a vector, which is a quantity containing both direction and magnitude (one, finite direction, not two).
The nuclear equation that describes the alpha decay of Polonium-210 can be written like this:
210/
84Po→206/82Pb+4/2 He
