Motion Direction
1. The problem asks us to determine whether the object is moving forward, backward, or neither at specific points on a position vs. time graph.
2. The key concept is that the direction of motion is indicated by the slope of the position-time graph at each point:
- If the slope (derivative) is positive, the object is moving forward (position increasing).
- If the slope is negative, the object is moving backward (position decreasing).
- If the slope is zero, the object is momentarily stationary (neither moving forward nor backward).
3. We analyze the slope around each given point:
- At (1, 2): The graph is rising before and after, so slope > 0, object moving forward.
- At (5, -1): The graph is falling before and after, so slope < 0, object moving backward.
- At (7, 2): The graph is rising before and after, so slope > 0, object moving forward.
- At (8.5, -4.5): The graph is falling before and after, so slope < 0, object moving backward.
4. Summary:
- (1, 2): Forward
- (5, -1): Backward
- (7, 2): Forward
- (8.5, -4.5): Backward
This interpretation uses the fundamental rule that the sign of the slope of the position-time graph indicates the direction of motion.