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 of the given speed-time (v-t) graphs is physically not possible, we need to analyze each option based on the fundamental properties of speed.

### Step-by-Step Solution:

1. **Understand the Concept of Speed**:
- Speed is a scalar quantity, meaning it only has magnitude and no direction. This means that speed cannot be negative; it can only be zero or positive.

2. **Analyze Option 1**:
- In the first graph, if we draw a vertical line at a specific time \( t \), we observe that there are three different speeds at that instant.
- Since a single object cannot have multiple speeds at the same time, this graph is not physically possible.

3. **Analyze Option 2**:
- Similarly, in the second graph, drawing a vertical line at a specific time \( t \) also reveals three different speeds for the same object.
- Again, this scenario is not possible, as an object cannot possess multiple speeds simultaneously.

4. **Analyze Option 3**:
- In the third graph, we notice that the speed values drop below zero, indicating negative speed.
- Since speed cannot be negative (it is a scalar quantity), this graph is also not physically possible.

5. **Conclusion**:
- Since all three options (1, 2, and 3) present scenarios that are not physically possible, the correct answer is that all of these graphs are invalid. Therefore, the correct option is option 4: all of these.