A brass disc fits snugly in a hole in a steel plate. Should you heat or cool the system to loosen the disc from the hole ? given that `alpha _b gt alpha _Fe`.

Explanation

To determine whether to heat or cool the system to loosen a brass disc snugly fitting in a hole in a steel plate, we need to consider the coefficients of linear expansion for both materials.

### Step-by-Step Solution:

1. **Understand the Problem**:
- We have a brass disc that fits snugly in a hole in a steel plate.
- The coefficient of linear expansion of brass (αB) is greater than that of steel (αFe).

2. **Define Coefficient of Linear Expansion**:
- The coefficient of linear expansion (α) indicates how much a material expands per degree of temperature change. A higher α means the material expands more for the same temperature increase.

3. **Heating the System**:
- If we heat the system, both the brass disc and the steel plate will expand.
- Since αB > αFe, the brass disc will expand more than the steel plate for the same temperature increase.
- Thus, the brass disc will still fit snugly in the hole, as it expands more than the steel.

4. **Cooling the System**:
- If we cool the system, both the brass disc and the steel plate will contract.
- Again, since αB > αFe, the brass disc will contract more than the steel plate for the same temperature decrease.
- This means that the brass disc will become smaller relative to the hole in the steel plate, thus loosening the fit.

5. **Conclusion**:
- To loosen the brass disc from the hole in the steel plate, we should **cool the system**. This is because the brass will contract more than the steel, allowing the disc to fit more loosely in the hole.

### Final Answer:
**Cool the system to loosen the brass disc from the hole.**

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