Which of the following speed - time (v - t) graphs is physically not possible?

Options

A.
B.
C.
D. All of these

Answer

To determine which speed-time (v-t) graph is physically not possible, we need to analyze the characteristics of speed and how it is represented in a graph.

### Step-by-Step Solution:

1. **Understanding Speed**:
- Speed is a scalar quantity, which means it has magnitude but no direction. It can only be zero or a positive value. Negative speed does not exist in the context of speed; it can only represent velocity, which is a vector quantity.

2. **Analyzing the Graphs**:
- **Graph 1**: If a graph shows multiple speeds at the same instant, it implies that the object is moving at different speeds simultaneously. This is not physically possible because an object can only have one speed at any given moment.
- **Graph 2**: Similar to Graph 1, if it indicates that the object has multiple speeds at the same time, it is also not possible for the same reason.
- **Graph 3**: If the graph shows negative speed, this is not possible because speed cannot be negative. It can only be zero or a positive value.
- **Graph 4**: If this graph does not show any of the above inconsistencies, it is likely the only valid graph.

3. **Conclusion**:
- Since all the first three graphs present scenarios that are not physically possible (multiple speeds at the same time or negative speed), we conclude that these graphs are invalid. Therefore, the correct answer is that all three graphs are not possible.

### Final Answer:
All three graphs (1, 2, and 3) are physically not possible.

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