Choose the correct statement(s).

Options

A. Speed and velocity both have same units.
B. If a body has a speed of 50 m `s^(-1)` in a straight line path, then its velocity is 180 km `h^(-1)`.
C. Speed of a vehicle is measured by a device called speedometer.
D. All of the above

Answer

To solve the question "Choose the correct statement(s)", we need to analyze the statements provided and determine their validity based on the principles of physics, particularly kinematics.

### Step-by-Step Solution:

1. **Understanding Speed and Velocity**:
- Speed is defined as the distance traveled per unit of time and is a scalar quantity, meaning it only has magnitude (no direction).
- Velocity, on the other hand, is defined as the displacement per unit of time and is a vector quantity, meaning it has both magnitude and direction.

**Hint**: Remember that scalar quantities do not involve direction, while vector quantities do.

2. **Units of Speed and Velocity**:
- Both speed and velocity are measured in the same units, typically meters per second (m/s) in the SI system. This means that the statement "Speed and velocity both have the same units" is true.

**Hint**: Units can be the same even if the quantities are different.

3. **Speed in a Straight Line**:
- If a body moves in a straight line, the distance traveled is equal to the displacement. Therefore, in this case, speed and velocity will have the same numerical value. For example, if a body has a speed of 50 m/s in a straight line, its velocity will also be 50 m/s in the same direction.

**Hint**: Consider the relationship between distance and displacement in straight-line motion.

4. **Conversion of Units**:
- To convert speed from meters per second to kilometers per hour, we multiply by the conversion factor \( \frac{18}{5} \). For instance, \( 50 \, \text{m/s} \times \frac{18}{5} = 180 \, \text{km/h} \). This confirms that both speeds are equivalent in different units.

**Hint**: Familiarize yourself with common unit conversion factors.

5. **Speed Measurement**:
- The speed of a vehicle is measured by a device called a speedometer. This device provides the instantaneous speed, which is the speed at a specific moment in time.

**Hint**: Recall the function of a speedometer in vehicles.

6. **Conclusion**:
- Since all the statements provided in the question are true, the correct answer is "All of the above".

### Final Answer:
- The correct option is **Option 4: All of the above**.