Question 1

A hydraulic lift in an auto repair shop uses Pascal's Principle to lift cars. If the area of the input piston is $$0.01\ \mathrm{m}^2$$ and the area of the output piston is $$0.5\ \mathrm{m}^2$$, what force must be applied to the input piston to lift a $$10,000\ \mathrm{N}$$ car?

Accepted Answer

$$200\ \mathrm{N}$$

Question 2

A swimmer dives to a depth of $$5\ \mathrm{m} in a $$freshwater lake. If the weight density of water is $$9800\ \mathrm{N/m}^3$$, what is the pressure due to the water at this depth (ignoring atmospheric pressure)?

Accepted Answer

$$49,000\ \mathrm{Pa}$$

Question 3

A block of aluminum and a block of lead have the same mass and are both fully submerged in water. Which block experiences the greater buoyant force and why?

Accepted Answer

The aluminum block, because it has a larger volume and displaces more water.

Question 4

A $$3\ \mathrm{kg}$$ block is submerged in water and appears to weigh $$2\ \mathrm{kg}. $$What is the magnitude of the buoyant force acting on the block?

Accepted Answer

$$9.8\ \mathrm{N}$$

Question 5

A boat floats higher in salt water than in fresh water. This is because:

Accepted Answer

Salt water is denser, so the buoyant force on the boat is greater for the same volume displaced.

Question 6

Which of the following best describes why a person lying on a bed of nails is not harmed?

Accepted Answer

The force is distributed over a large area, reducing the pressure on any single point.

Question 7

A fish adjusts its buoyancy by expanding its air bladder. What happens to its density and the buoyant force acting on it?

Accepted Answer

Its density decreases and the buoyant force increases.

Question 8

A $$2\ \mathrm{kg}$$ object floats in water. What is the weight of the water displaced by the object?

Accepted Answer

$$19.6\ \mathrm{N}$$

Question 9

Which of the following statements about pressure in a liquid is correct?

Accepted Answer

Pressure at a given depth depends only on the depth and the liquid’s density, not on the shape of the container.

Question 10

A hydraulic press has an input piston with area $$A$$ and an output piston with area $$10A. If a $$force $$F is $$applied to the input piston, what is the force on the output piston?

Accepted Answer

$$10F$$

Question 11

Which of the following best explains why drops of water are spherical?

Accepted Answer

Surface tension minimizes the surface area for a given volume, forming a sphere.

Question 12

Which of the following will increase the capillary rise of water in a tube?

Accepted Answer

Decreasing the diameter of the tube.

Question 13

A block is completely submerged in a liquid and is at rest. Which forces act on the block?

Accepted Answer

The buoyant force upward and the force of gravity downward.

Question 14

A life preserver filled with lead pellets provides a greater buoyant force than one filled with Styrofoam. Why is the lead-filled preserver not safe?

Accepted Answer

Its weight is much greater than the buoyant force, so it will sink.

Question 15

Which of the following is NOT a factor that affects surface tension?

Accepted Answer

The color of the liquid.

Question 16

A $$5\ \mathrm{kg}$$ object is fully submerged in a fluid with a density greater than water. Compared to being submerged in water, the buoyant force on the object is:

Accepted Answer

Greater, because the denser fluid displaces more weight per volume.

Question 17

Which of the following is a correct application of Pascal’s Principle?

Accepted Answer

A dentist’s chair is raised by applying pressure to a small piston, which is transmitted to a larger piston.

Question 18

If you stand on one foot instead of two, what happens to the pressure you exert on the floor?

Accepted Answer

It increases, because the same force is applied over a smaller area.

Question 19

Which of the following best describes the condition for an object to float in a liquid?

Accepted Answer

The weight of the object equals the buoyant force exerted by the liquid.

Chapter 13: Liquids – Physics with Calculus Study Notes

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