Question

In front of a door, there is a very heavy bookcase. A boy decides to shove it out of the way, so he stands next to it and begins to push. However, instead of moving it, he begins to move backward. Why does this happen? (im guessing because the bookcase is pushing back on him with a force equal to the one he exerted? not sure)

Answer 1

When the boy pushes the bookcase, he moves backward instead of moving the bookcase.

According to Newton's law,

`F=(dp)/(dt)`

Here, p is momentum which is equal to mass times velocity.

Also, According to Newton's third law, the bookcase also applies equal force on the boy.

As the mass of the bookcase is heavier than the mass of the boy.

Thus, the boy moves backward instead of pushing back the bookcase.