Question 1

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) True
B) False

Accepted Answer

According to the principle of continuity for incompressible fluids, the flow rate must remain constant throughout the pipe. Therefore, the same amount of water flows per second through both the wide and narrow sections.

Question 2

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

E

Question 3

A 0.600-mm diameter wire stretches 0.500% of its length when it is stretched with a tension of 20.0 N. What is the Young's modulus of this wire? A) 5.66 × 10¹⁰ N/m² B) 3.54 × 10⁹ N/m² C) 1.41 × 10¹⁰ N/m² D) 6.43 × 10⁹ N/m² E) 2.78 × 10⁹ N/m²

Accepted Answer

Young's modulus can be calculated using the equation:
Y = (F/A)/(ΔL/L)
where F is the force applied, A is the cross-sectional area of the wire, ΔL is the change in length, and L is the original length of the wire.
First, we need to calculate the cross-sectional area of the wire. The diameter is 0.600 mm, so the radius is 0.300 mm. Therefore, the cross-sectional area is:
A = πr^2 = π(0.300 mm)^2 = 0.2827 mm^2
Next, we can substitute the given values into the equation for Y:
Y = (F/A)/(ΔL/L) = (20.0 N)/(0.2827 mm^2)/(0.005) = 1.41 × 10^11 N/m^2 
Therefore, the Young's modulus of the wire is 1.41 × 10^11 N/m^2, which corresponds to choice C.

Question 4

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 5

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 cube melts, it turns into water which has the same volume as the ice cube. Therefore, there is no change in the water level and it remains the same.

Question 6

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 applied force per cross-sectional area, which means it has units of force/area (such as N/m² or Pa). Option A is the definition of strain, option B is not correct as stress and force are not the same, option C refers to the strain, not stress, and option E is the definition of elastic modulus.

Question 7

Tensile strain 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

Tensile strain is defined as the ratio of the change in length (∆L) to the original length (L). It is a measure of the deformation of a material due to an applied force or stress.

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

According to Bernoulli's principle, as the speed of a fluid increases, the pressure within the fluid decreases. This is due to the fact that as the fluid moves faster, the molecules within the fluid have less time to collide with each other and the walls of the container, resulting in a decrease in pressure. Therefore, choice C is the correct answer.

Question 9

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

Buoyant force depends on the displaced volume of fluid, which is equal to the volume of the submerged portion of the object. As the block of iron is totally submerged, its volume of submerged portion is greater than the volume of submerged portion of the block of wood which is only partially submerged. Therefore, the buoyant force acting on the block of iron is greater than the buoyant force acting on the block of wood.

Question 10

A cable is 100 m long, has a cross-sectional area of 1.0 mm², and is made of a material having a Young's modulus of 1.0 × 10¹¹ N/m². If a 1000-N force is applied to stretch the cable, how far does it stretch? A) 0.0010 m B) 0.010 m C) 0.10 m D) 1.0 m E) 10 m

Accepted Answer

The answer of A cable is 100 m long, has...

Question 11

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 12

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 volume of the wood that was already in the tub displaces a certain amount of water, which is equal to its own volume. When the second piece of wood is placed on top, it doesn't displace any additional water. Therefore, when it is removed and placed in the water, it displaces the same amount of water as it did before, and the water level remains unchanged.

Question 13

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 14

A steel guitar string with a diameter of 0.300 mm and a length of 70.0 cm is stretched by 0.500 mm while being tuned. How much force is needed to stretch the string by this amount? Young's modulus for steel is 2.0 × 10¹¹ N/m².

Accepted Answer

The answer of A steel guitar string with a diameter...

Question 15

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 buoyant force on a stone placed in water only depends on the weight of water displaced by the stone, and is not affected by the external pressure applied to the water. Therefore, doubling the pressure on the surface of the can of water will not change the buoyant force on the stone.

Question 16

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 related to the change in volume of sphere one ? A) ΔV₂=2ΔV₁ B) ΔV₂= 4ΔV₁ C) ΔV₂=ΔV₁ D) ΔV₂= 1/2ΔV₁ E) ΔV₂= 1/4ΔV₁

Accepted Answer

The answer of Two compressible solids are formed into spheres...

Question 17

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 18

A 1000-kg object hangs from the lower end of a steel rod 5.0 m long that is suspended vertically. The diameter of the rod is 0.80 cm and Young's modulus for the rod is 210,000 MN/m². What is the elongation of the rod due to this object? A) 1.2 cm B) 0.46 cm C) 0.12 cm D) 1.8 cm E) 0.047 cm

Accepted Answer

First, we must calculate the cross-sectional area of the steel rod:
Area = π(r^2) = π(0.80/2)^2 = 0.5027 mm^2

Next, we can calculate the force exerted on the rod by the object:
F = mg = (1000 kg)(9.81 m/s^2) = 9810 N

Then, we can calculate the stress on the steel rod:
Stress = F/A = (9810 N)/(0.5027 mm^2) = 1.95 x 10^7 N/m^2

Using Young's modulus, we can find the strain of the steel rod:
Strain = Stress/E = (1.95 x 10^7 N/m^2)/(210,000 MN/m^2) = 0.0000933

Finally, we can find the elongation of the steel rod:
Elongation = Strain x Length = (0.0000933)(5.0 m) = 0.0004665 m = 0.04665 cm

So the answer is B, 0.46 cm (rounded to two decimal places).

Question 19

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, it creates a region of low pressure. This is known as the Bernoulli principle. In this case, the air above the upper face of the paper is moving faster than the air below the paper, creating a region of low pressure above the paper. This low pressure causes the paper to rise.

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

The answer of The graph in the figure shows the...

Quiz 14: Fluids and Elasticity

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.

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

A 0.600-mm diameter wire stretches 0.500% of its length when it is stretched with a tension of 20.0 N. What is the Young's modulus of this wire?

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

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

Tensile stress is

Tensile strain is

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

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 cable is 100 m long, has a cross-sectional area of 1.0 mm2, and is made of a material having a Young's modulus of 1.0 × 1011 N/m2. If a 1000-N force is applied to stretch the cable, how far does it stretch?

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 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?

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 steel guitar string with a diameter of 0.300 mm and a length of 70.0 cm is stretched by 0.500 mm while being tuned. How much force is needed to stretch the string by this amount? Young's modulus for steel is 2.0 × 1011 N/m2.

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

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 1000-kg object hangs from the lower end of a steel rod 5.0 m long that is suspended vertically. The diameter of the rod is 0.80 cm and Young's modulus for the rod is 210,000 MN/m2. What is the elongation of the rod due to this object?

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

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?

A cable is 100 m long, has a cross-sectional area of 1.0 mm², and is made of a material having a Young's modulus of 1.0 × 10¹¹ N/m². If a 1000-N force is applied to stretch the cable, how far does it stretch?

A steel guitar string with a diameter of 0.300 mm and a length of 70.0 cm is stretched by 0.500 mm while being tuned. How much force is needed to stretch the string by this amount? Young's modulus for steel is 2.0 × 10¹¹ N/m².

A 1000-kg object hangs from the lower end of a steel rod 5.0 m long that is suspended vertically. The diameter of the rod is 0.80 cm and Young's modulus for the rod is 210,000 MN/m². What is the elongation of the rod due to this object?