A displacement is a change in position. Displacement can have positive and negative values, as can position. When negative is defined to be left of the origin, a negative displacement is to the left. A positive displacement is to the right. The position of an object is equal to the position it starts plus the displacement it moves.
A ball moves a displacement of −20 meters from where it is in the diagram. Which of the following is TRUE?
- The ball moves a total distance of −30 m.
- The ball moves a total distance of 30 m.
- The ball ends up at a position of −30 m.
- The ball ends up at a position of +10 m.
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The answer is c, the ball ends up at a position of −30 m. The ball begins at a position of −10 m. If it moves another −20 m from where it begins, it will end up at: −10 + (−20) = −30 m
It doesn't matter what path the ball takes to get there, but it does end up 20 m to the left of where it started.
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