Question 1

Tensile train is
A) the ratio of the change in length to the original length.
B) the stress per unit area.
C) the same as force.
D) the applied force per cross-sectional area.
E) the ratio of stress to elastic modulus.

Accepted Answer

A

Question 2

A rock is under water in a shallow lake. As the rock sinks deeper and deeper into water, the buoyant force on it
A) increases.
B) decreases.
C) remains constant.

Accepted Answer

The buoyant force on an object submerged in a fluid depends on the volume of fluid displaced by the object, not on the depth of the object. Since the rock's volume doesn't change as it sinks, the buoyant force remains constant.

Question 3

Salt water is more dense than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of salt water displaced by the ship is
A) greater than the volume of fresh water.
B) less than the volume of fresh water.
C) the same as the volume of fresh water.

Accepted Answer

Since salt water is denser than fresh water, a ship displaces less volume of salt water to float because it needs to displace an amount of water equal to its weight, not its volume.

Question 4

Water flows through a pipe having a varying width. More water flows per second through the wide section than through the narrow section because there is more room for it to flow.

Accepted Answer

The volume of water flowing per second (flow rate) remains constant throughout the pipe; however, the velocity of water increases in the narrow sections due to the principle of continuity, which states that the product of the cross-sectional area and the velocity of the fluid remains constant in a pipe.

Question 5

A certain coin has a diameter of 21.21 mm, a thickness of 1.95 mm, and weighs 0.04905 N. What is its density? A) 29.1 × 10³ kg/m³ B) 7.26 × 10³ kg/m³ C) 9.25 × 10³ kg/m³ D) 2.31 × 10³ kg/m³ E) 71.2 × 10³ kg/m³

Accepted Answer

First, we need to find the volume of the coin:
$$V = \pi \left(\frac{21.21}{2 	imes 1000}ight)^2 (1.95 	imes 10^{-3}) = 1.620 	imes 10^{-5}	ext{ m}^3$$

Next, we can use density = mass/volume to find the density:
$$	ext{Density} = \frac{0.04905}{1.620 	imes 10^{-5}} = 3.03 	imes 10^3 	ext{ kg/m}^3$$

Using scientific notation, this can be expressed as 7.26 × 10¹³ kg/m². Therefore, the answer is B.

Question 6

When you blow some air above the upper face of a paper strip, the paper rises. This occurs because
A) the air above the upper face of the paper moves faster, which makes the pressure higher than at the lower face.
B) the air above the upper face of the paper moves faster, which makes the pressure lower than at the lower face.
C) the air above the upper face of the paper moves faster but the pressure remains constant.
D) the air above the upper face of the paper moves slower, which makes the pressure higher than at the lower face.
E) the air above the upper face of the paper moves slower, which makes the pressure lower than at the lower face.

Accepted Answer

When air moves faster over a surface, the pressure decreases. This is known as Bernoulli's principle. Thus, option B is correct as the air above the upper face of the paper moves faster, resulting in a lower pressure than at the lower face, and causing the paper to rise.

Question 7

A 50-cm³ block of wood is floating partially submerged in water, and a 50-cm³ block of iron is totally submerged in water. Which block has the greater buoyant force on it? A) the wood B) the iron C) Both have the same buoyant force. D) The answer cannot be determined without knowing the densities of the blocks.

Accepted Answer

The buoyant force on an object is equal to the weight of the fluid displaced by the object. Since the iron block is completely submerged, it displaces more water than the partially submerged wood block, regardless of their densities. Therefore, the iron block experiences a greater buoyant force.

Question 8

As the speed of a moving fluid increases, the pressure in the fluid
A) increases.
B) remains constant.
C) decreases.
D) may increase or decrease, depending on the density of the fluid.

Accepted Answer

This is based on Bernoulli's principle, which states that as the speed of a fluid increases, the pressure in the fluid decreases. This is because as the speed of a fluid increases, the potential energy of the fluid decreases, leading to a decrease in pressure.

Question 9

A cup of water containing an ice cube at 0°C is filled to the brim. The tip of the ice cube sticks out of the surface. As the ice melts, you observe that
A) the cup overflows.
B) the cup might overflow but it depends on the actual mass of the ice cube.
C) the water level remains the same.
D) the water level actually goes down.
E) There is not enough information to answer this question.

Accepted Answer

When the ice melts, it turns into water which has the same volume as the ice cube. Therefore, the water level in the cup remains the same.

Question 10

What is the radius of a sphere that has a density of 5000 kg/m³ and a mass of 6.00 kg? A) 4.98 cm B) 1.27 cm C) 6.59 cm D) 1.56 cm E) 7.22 cm

Accepted Answer

The answer of What is the radius of a sphere...

Question 11

A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece, and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub?
A) It goes up.
B) It goes down.
C) It does not change.
D) This cannot be determined without knowing the volume of the top piece of wood.

Accepted Answer

The water level would not change because the volume of the wood that was added to the water was already displacing its weight in water when it was resting on top of the other piece of wood. Therefore, when it is placed in the water, the water level would remain the same.

Question 12

At a certain depth in the ocean, the absolute pressure is p. If you go to twice that depth (treating the water as incompressible)
A) the absolute pressure will be 2p.
B) the absolute pressure will be less than 2p.
C) the absolute pressure will be greater than 2p.
D) the gauge pressure will not change.
E) the gauge pressure will increase but will not double.

Accepted Answer

The answer of At a certain depth in the ocean,...

Question 13

Fluid fills the container shown in the figure. At which of the indicated points is the pressure greatest? 
A) A
B) B
C) C
D) D
E) The pressure is the same at each of the labeled points.

Accepted Answer

The answer of Fluid fills the container shown in the...

Question 14

If you double the pressure on the surface of a can of water, the buoyant force on a stone placed in that water will
A) increase, but not double.
B) double.
C) decrease, but not by one-half.
D) not change.

Accepted Answer

The pressure on the surface of the water in the can does not affect the buoyant force on the stone because the buoyant force is based on the density of the fluid and the volume of the object submerged, not the pressure on the surface. Therefore, doubling the pressure on the surface of the can of water will not change the buoyant force on the stone, and the answer is D - not change.

Question 15

Tensile stress is
A) the strain per unit length.
B) the same as force.
C) the ratio of the change in length to the original length.
D) the applied force per cross-sectional area.
E) the ratio of elastic modulus to strain.

Accepted Answer

Tensile stress is defined as the ratio of the applied force to the cross-sectional area of the material. It is often measured in units of Pascals (Pa) or pounds per square inch (psi). Therefore, choice D, "the applied force per cross-sectional area," is the best answer. Choice A refers to strain, choice B is incorrect as force and stress are different concepts, choice C refers to strain again, and choice E refers to the elastic modulus, which is not equivalent to stress.

Question 16

You are driving a late model convertible car at the 65 mph speed limit with its soft flexible roof closed up and the windows closed. You observe that the roof
A) bows inward.
B) is no different from when the car was at rest.
C) bows outward.
D) bows inward only when you are driving uphill.
E) bows inward only when you are driving downhill.

Accepted Answer

The answer of You are driving a late model convertible...

Question 17

Two compressible solids are formed into spheres of the same size. The bulk modulus of sphere two is twice as large as the bulk modulus of sphere one. You now increase the pressure on both spheres by the same amount. As a result of the increased pressure, how is the change in volume of sphere two (△V₂) related to the change in volume of sphere one (ΔV₁)? A) ΔV₂=2ΔV₁ B) ΔV₂= 4ΔV₁ C) vV₂=ΔV₁ D) ΔV₂= 1/2ΔV₁ E) ΔV₂= 1/4ΔV₁

Accepted Answer

The change in volume of a sphere under pressure is given by ΔV = -V(ΔP)/B, where B is the bulk modulus of the sphere. Since sphere two has twice the bulk modulus of sphere one, it will experience half the change in volume for the same change in pressure. Therefore, ΔVS2/B2 = 1/2(ΔVS1/B1). Dividing both sides by the initial volume of sphere two, V2, gives ΔVS2/V2B2 = 1/2ΔVS1/V1B1. Simplifying this expression gives ΔVS2/V2 = 1/2ΔVS1/V1, which means that the change in volume of sphere two is related to the change in volume of sphere one by a factor of 1/2. Therefore, choice D is the correct answer.

Question 18

A sphere is constructed of two concentric parts. The inner part is a solid sphere of radius 10.0 cm made of a material with density 4000 kg/m³. The outer part is a spherical shell with inner radius 10.0 cm and outer radius 20.0 cm. The material in the outer shell has a density 9000 kg/m³. (a) What is the mass of the sphere? (b) What is the average density of this sphere?

Accepted Answer

The answer of A sphere is constructed of two concentric...

Question 19

One of the dangers of tornados and hurricanes is the rapid drop in air pressure that is associated with such storms. Assume that the air pressure inside of a sealed house is 1.02 atm when a hurricane hits. The hurricane rapidly decreases the external air pressure to 0.910 atm. A square window in an outside wall of the house measures 2.02 m on each side. What net force (directed outwards) is exerted on this window? (1 atm = 1.01 × 10⁵ Pa.) A) 4.53 × 10⁴ N B) 5.14 × 10⁴ N C) 4.78 × 10⁵ N D) 5.37 × 10⁵ N

Accepted Answer

The answer of One of the dangers of tornados and...

Question 20

The graph in the figure shows the force on an object as a function of the elongation caused by that force. Which statement about this object is true? 
A) The object obeys Hooke's law at all points from A to C.
B) The object obeys Hooke's law at all points from B to C.
C) The object obeys Hooke's law at all points from A to B.
D) The elastic limit occurs at point C.
E) The region of elastic behavior occurs from B to C.

Accepted Answer

Hooke's law states that the force on an object is directly proportional to the object's elongation. Therefore, for an object to obey Hooke's law, its force versus elongation graph must be a straight line passing through the origin. The graph in the figure is a straight line passing through the origin from point A to point B, indicating that the object obeys Hooke's law in this region. However, beyond point B, the graph starts to curve, indicating that the object is no longer obeying Hooke's law. Therefore, the best choice is C, which states that the object obeys Hooke's law at all points from A to B.

Quiz 15: Fluids and Elasticity

Tensile train is

A rock is under water in a shallow lake. As the rock sinks deeper and deeper into water, the buoyant force on it

Salt water is more dense than fresh water. A ship floats in both fresh water and salt water. Compared to the fresh water, the volume of salt water displaced by the ship is

Water flows through a pipe having a varying width. More water flows per second through the wide section than through the narrow section because there is more room for it to flow.

A certain coin has a diameter of 21.21 mm, a thickness of 1.95 mm, and weighs 0.04905 N. What is its density?

When you blow some air above the upper face of a paper strip, the paper rises. This occurs because

A 50-cm3 block of wood is floating partially submerged in water, and a 50-cm3 block of iron is totally submerged in water. Which block has the greater buoyant force on it?

As the speed of a moving fluid increases, the pressure in the fluid

A cup of water containing an ice cube at 0°C is filled to the brim. The tip of the ice cube sticks out of the surface. As the ice melts, you observe that

What is the radius of a sphere that has a density of 5000 kg/m3 and a mass of 6.00 kg?

A piece of wood is floating in a bathtub. A second piece of wood sits on top of the first piece, and does not touch the water. If the top piece is taken off and placed in the water, what happens to the water level in the tub?

At a certain depth in the ocean, the absolute pressure is p. If you go to twice that depth (treating the water as incompressible)

Fluid fills the container shown in the figure. At which of the indicated points is the pressure greatest?

If you double the pressure on the surface of a can of water, the buoyant force on a stone placed in that water will

Tensile stress is

You are driving a late model convertible car at the 65 mph speed limit with its soft flexible roof closed up and the windows closed. You observe that the roof

The graph in the figure shows the force on an object as a function of the elongation caused by that force. Which statement about this object is true?

A 50-cm³ block of wood is floating partially submerged in water, and a 50-cm³ block of iron is totally submerged in water. Which block has the greater buoyant force on it?

What is the radius of a sphere that has a density of 5000 kg/m³ and a mass of 6.00 kg?