practice problem 1
- a book lying on a level table.
- a person floating in still water.
- a wrecking ball hanging vertically from a cable.
- a helicopter hovering in place.
In all four cases, the downward pull of gravity is balanced by an upward force. There are no significant lateral (side-to-side) forces in these examples. Read the discussion section of this topic for a more detailed explanation.
practice problem 2
The solution to this problem depends on the direction of the acceleration of the wagon. Read the discussion section of this topic for a more detailed explanation.