Archimedes' principle states that upthrust equals the weight of which of the following? Also, what happens to the viscosity of liquids as temperature increases?

For a floating object, the weight of the object is equal to the upthrust. The upthrust is equal to the weight of the fluid displaced.
Weight of object ($W_o$) = $\rho_o V_o g$
Upthrust ($F_B$) = Weight of fluid displaced = $\rho_f V_{sub} g$
Since the object is floating, $W_o = F_B$.

$$\rho_o V_o g = \rho_f V_{sub} g$$

Divide both sides by $g$:

$$\rho_o V_o = \rho_f V_{sub}$$

The fraction submerged is the ratio of the submerged volume ($V_{sub}$) to the total volume of the object ($V_o$).

$$\frac{V_{sub}}{V_o} = \frac{\rho_o}{\rho_f}$$

Given:

• Density of wood ($\rho_o$) = $600 \text{ kg/m}^3$
• Density of water ($\rho_f$) = $1000 \text{ kg/m}^3$

$$\frac{V_{sub}}{V_o} = \frac{600 \text{ kg/m}^3}{1000 \text{ kg/m}^3}$$ $$\frac{V_{sub}}{V_o} = 0.6$$

The fraction of the wood submerged is 0.6.

The correct option is B.

$$\boxed{\text{B. } 0.6}$$

As temperature increases, the viscosity of most liquids decreases. This is because the increased kinetic energy of the molecules allows them to overcome intermolecular forces more easily, reducing resistance to flow.

The correct option is B.

$$\boxed{\text{B. Decreases}}$$

The stretched elastic skin behavior of liquids is called surface tension. This phenomenon arises from the cohesive forces between liquid molecules, which cause the surface to behave like a stretched elastic membrane.

The correct option is C.

$$\boxed{\text{C. Surface tension}}$$

Standard atmospheric pressure is $760 \text{ mmHg}$, which is equivalent to $1 \text{ atmosphere}$.
The conversion factor for $1 \text{ atmosphere}$ to Pascals is approximately $1.01325 \times 10^5 \text{ Pa}$.

Given:

• Pressure = $760 \text{ mmHg}$

Since $760 \text{ mmHg}$ is exactly $1 \text{ atmosphere}$, its approximate value in Pascals is $1.01 \times 10^5 \text{ Pa}$.

The correct option is A.

$$\boxed{\text{A. } 1.01 \times 10^5 \text{ Pa}}$$