Question 1: Determine the length of the feather. Step 1: Read the starting point of the feather on the ruler. The feather starts at the 10 mm mark (or 1.0 cm). Step 2: Read the ending point of the fea

The feather starts at the 10 mm mark (or 1.0 cm).

The feather ends at the 28 mm mark (or 2.8 cm).

Length = Ending point - Starting point

The final answer is $\boxed{18 \text{ mm}}$.

Object X causes a smaller extension of its spring.
Object Y causes a larger extension of its spring.

Since the springs are identical, a larger extension indicates a greater force (weight) acting on the spring. Therefore, object Y has a greater weight than object X.

Weight is directly proportional to mass ($W = mg$). Since object Y has a greater weight, it must also have a greater mass than object X.

Comparison:

• Object Y has a greater weight than object X.
• Object Y has a greater mass than object X.

Volume of oil ($V$) = 750 cm³
Mass of bottle + oil = 650 g
Mass of empty bottle = 50 g

Density ($\rho$) is calculated using the formula $\rho = \frac{\text{Mass}}{\text{Volume}}$.

The final answer is $\boxed{0.8 \text{ g/cm}^3}$.