An object is placed at 0 on a number line. it moves 3 units to the right, then 4 units to the left, and then 6 units to the right. the displacement of the object is

With reference to the point 0, let's assign positive to right of zero and negative to left of zero. In this case, the object moves as follows;
1. 3 units to the right: +3 = initial school
2. 4 units to the left: 3-4 = -1
3. 6 units to the right: -1+6 = +5 = final position
The displacement of the object will be final position - initial position = 5-3 = 2

Your displacement will be:

3-4+6 = 5. The positive sign means the direction is to the right

Iwould choose the same momentum because if they throw a baseball very light and not hard at all then doing it with a bowling ball won’t hurt that worse