Question 1

According to Pascal’s Principle, what happens when a force is applied to an enclosed fluid?

Accepted Answer

The pressure change is transmitted undiminished throughout the entire fluid.

Question 2

A hydraulic lift uses two pistons with areas $$A_1$$ and $$A_2. If a $$force $$F_1 is $$applied to the smaller piston, what is the force $$F_2$$ exerted by the larger piston, assuming both pistons are at the same height?

Accepted Answer

$$F_2$$ = $$F_1$$ \frac{$$A_2$$}{$$A_1$$}$$

Question 3

A car weighing 20,500 N is lifted by a hydraulic lift. The input piston has a radius of $$0.0120\,m$$ and the output piston has a radius of $$0.150\,m. $$What input force $$F_1 is $$required to lift the car?

Accepted Answer

$$F_1 = 131$$\,N$$

Question 4

Which of the following best describes the buoyant force acting on a submerged object?

Accepted Answer

It is equal to the weight of the fluid displaced by the object.

Question 5

A solid object is completely submerged in water. If the object’s density is less than that of water, what will happen when it is released?

Accepted Answer

It will float to the surface.

Question 6

Which equation correctly expresses Archimedes’ Principle for the buoyant force $$F_B on a $$submerged object?

Accepted Answer

$$F_B = \rho_{fluid} V_{displaced} g$$

Question 7

A pinewood raft is $$4.0\,m on $$each side and $$0.30\,m$$ thick. If the density of pine is $$550\,kg/m^3$ and water is 1000$$\,$$kg/m^3$$, how much of the raft’s thickness is submerged when floating?

Accepted Answer

$$0.17\,m$$

Question 8

If an object is neutrally buoyant in a fluid, which of the following must be true?

Accepted Answer

The object’s density is equal to the fluid’s density.

Question 9

A diver finds that a rock appears lighter when submerged in water. Which principle explains this observation?

Accepted Answer

Archimedes’ Principle

Question 10

A piston system has input area $$A_1 = 0.001$$\,$$m^2$$ and output area $$A_2 = 0.1$$\,$$m^2. If an $$input force of $$50\,N is $$applied, what is the output force?

Accepted Answer

$$F_2 = 5$$,000\,N$$

Question 11

Which of the following is NOT a requirement for Pascal’s Principle to apply?

Accepted Answer

The fluid must be a gas.

Question 12

A block of unknown material floats with half its volume submerged in oil of density $$800\,kg/m^3$. What is the density of the block?

Accepted Answer

$$400\,kg/m^3$

Question 13

If the pressure at a certain depth in a fluid is $$P$$, what happens to the pressure if the depth is doubled, assuming constant density?

Accepted Answer

The pressure doubles.

Question 14

A submarine is designed to achieve neutral buoyancy in seawater. What must be true about the mass of water displaced by the submarine?

Accepted Answer

It is equal to the mass of the submarine.

Question 15

A cube of side $$0.10\,m is $$completely submerged in a fluid of density $$900\,kg/m^3$. What is the magnitude of the buoyant force acting on the cube? (Take g = 9.8$$\,$$m/s^2)$$

Accepted Answer

$$8.82\,N$$

Question 16

Which of the following real-world devices best demonstrates Pascal’s Principle?

Accepted Answer

A hydraulic car lift

Fluids: Pascal’s Principle and Archimedes’ Principle- lecture 21

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