Energy cannot be measured in

Options

A. Js
B. Ws
C. kWh
D. erg

Answer

To solve the question "Energy cannot be measured in," we need to analyze the options provided and determine which one does not represent a unit of energy.

### Step-by-Step Solution:

1. **Understand the Units of Energy**:
- Energy is commonly measured in joules (J).
- Other units of energy include kilowatt-hours (kWh) and calories.

2. **Analyze Each Option**:
- **Option 1: Joule into second (J·s)**:
- This unit represents angular momentum, not energy. Therefore, it is not a valid unit of energy.
- **Option 2: Watt into second (W·s)**:
- A watt is defined as one joule per second (1 W = 1 J/s). Therefore, watt into second (W·s) is equivalent to joules (1 W·s = 1 J). This is a valid unit of energy.
- **Option 3: Kilowatt (kW)**:
- A kilowatt is a unit of power, which is the rate of energy transfer. It is not a direct measure of energy itself.
- **Option 4: Arc**:
- This is not a standard unit of energy. It seems to be an incorrect or misrepresented term.

3. **Conclusion**:
- The only option that cannot be used to measure energy directly is **Option 1: Joule into second (J·s)**, as it represents angular momentum.

### Final Answer:
Energy cannot be measured in **Joule into second (J·s)**.