Physics Chapter 13

The pressure in a liquid depends on liquid

-depth -density

An egg rests at the bottom of a bowl filled with water. When salt is slowly added to the water the egg rises and floats, from which we conclude

-salt water is denser than an egg -salt water is denser than fresh water

A fish normally displaces its own

-weight of water -volume of water

If a 1-L container is immersed halfway into water, what is the volume of the water displaced? What is the buoyant force on the container?

0.5 L displaced, 5 N buoyant force

If an object suspended by a scale shows a weight of 3 N in air, and 2 N when submerged in water, the buoyant force on the submerged object is __________.

1 N

What is the mass of 1 L of water? What is its weight in newtons?

1 kg; 10 N

One liter of water has a mass of

1 kilogram

Buoyant force is greater on a submerged

1-kg block of aluminum

The buoyant force acting on a 10-ton ship floating in the ocean is

10 tons

How much air must a 100-ton blimp displace to float and neither rise nor sink?

100 tons

What is the weight of water displaced by a 100-ton floating ship?

100 tons

The mass of a cubic meter of water is

1000 kg

In lab you find that a 1-kg rock suspended above water weighs 10 N . When the rock is suspended beneath the surface of the water, the scale reads 8.0 N. If the container of water weighs 10 N on the weighing scale, what is the scale reading when the rock is suspended beneath the surface of the water?

12 N -If the container of water on a bathroom-type scale weighs 9.8 N, what is the scale reading when the rock is suspended beneath the surface of the water? Newton's third law says that if the water pushes the rock up then the rock pushes down on the water with an equal and opposite force. Therefore the rock pushes down on the water with a force of 2N. When this is added to the initial scale reading we get 11.8 N

A scale from which a rock is suspended reads 5 N when the rock is out of water and 3 N when the rock is submerged. Buoyant force on the rock is

2 N

In lab you find that a 1-kg rock suspended above water weighs 10 N . When the rock is suspended beneath the surface of the water, the scale reads 8.0 N. What is the buoyant force on the rock?

2 N -Two forces are acting upwards on the rock, the hook scale and the upthrust. The sum of these two forces must balance the weight of the rock, 9.8 N. Therefore the upthrust = 9.8N - 7.8N = 2N

In lab you find that a 1-kg rock suspended above water weighs 10 N . When the rock is suspended beneath the surface of the water, the scale reads 8.0 N. What is the scale reading when the rock is released and rests at the bottom of the container?

20 N -What is the scale reading when the rock is released and rests at the bottom of the container? When the rock is released the spring balance will have to support the weight of the rock as well as the weight of the water and container, bringing the reading to 9.8N + 9.8N = 19.6N

How much force is needed to hold a nearly weightless but rigid 1-L carton beneath the surface of water?

9.8N

How is the density of a fish controlled? How is the density of a submarine controlled?

A fish changes its volume, whereas a submarine changes its weight

Why isn't there a horizontal buoyant force on a submerged object?

Force vectors on the sides cancel one another

Is the buoyant force on a submerged object equal to the weight of the object itself or is it equal to the weight of the fluid displaced by the object?

It is equal to the weight of the fluid displaced

When Dr. Hewitt immerses the object in water, how does the loss of weight of the object compare with the buoyant force of the water?

Loss of weight is equal to the buoyant force

What is the cause of surface tension?

Molecular attraction

How does pressure relate to force?

Pressure is force per unit area

What is the relationship between liquid pressure and the depth of a liquid? Between liquid pressure and weight density?

Pressure is proportional to both depth and weight density

What will these objects do in water: an object denser than water, an object less dense than water, an object that has the same density as water.

Sink, float, neither float nor sink

What geometrical shape has the smallest surface area for a given volume?

Sphere

The attraction between unlike substances is called

adhesion

Water pressure in a lake is greater __________.

at the bottom

Water pressure on a submerged object is greatest against its

bottom

On what factors does the buoyant force acting on an object depend?

height of the object

When a boat sails from fresh water to salt water, the boat will float

higher in the water

If you float a piece of wood in a container half-full of water that rests on a weighing scale, the weight reading on the scale will

increase

The volume of water displaced by a floating 20-ton boat

is the volume of 20 tons of water

Buoyant force is greater on a submerged 1-cubic centimeter block of

lead and aluminum - same on each

A block of aluminum with a mass of 1 kg is placed in a beaker of water filled to the brim. Water overflows. The same is done in another beaker with a 1-kg block of lead. Does the lead displace more, less, or the same amount of water?

less

A lobster crawls onto a bathroom scale on the ocean floor. Its weight compared to its weight above the surface is

less

The amount of water displaced by a liter-sized block of ordinary wood floating in water is

less than 1 liter

Pumice is a volcanic rock that floats, which means its density is

less than the density of water

A person floats higher in the dense water of the Dead Sea because

less volume of water is displaced

Compared to an empty ship, the same ship loaded with Styrofoam will float

lower in the water

Surface tension is caused by __________.

molecular attractions

Buoyant force acts upward on a submerged object because

pressure against its bottom is greater than pressure against its top

An ice cube floating in a glass of water contains many air bubbles. When the ice melts, the water level will

remain unchanged

If you float a piece of wood in a container brim-full of water that rests on a weighing scale, some water will spill. Then the weight reading on the scale will

remain unchanged

Two life preservers have identical volumes, but one is filled with Styrofoam while the other is filled with sand. When the two life preservers are fully submerged, the buoyant force is greater on the one filled with

same on each as long as their volumes are the same

The pressure at the bottom of a jug filled with water does NOT depend on

surface area of the water

When holes are drilled through the wall of a water tower, water will spurt out with the greatest speed from the hole closest to

the bottom of the tower

The reason a life jacket helps keep you afloat is

the density of both you and the jacket together is less than your density alone

Compared to the density of water, the density of a fish is

the same

A block of aluminum with a volume of 10 cm3 is placed in a beaker of water filled to the brim. Water overflows. The same is done in another beaker with a 10-cm3 block of lead. Does the lead displace more, less, or the same amount of water?

the same amount

When you stand with only one of your feet on a weighing scale, the scale reading is

the same as with both feet

A completely submerged object always displaces its own

volume of fluid

A hospital patient confined to bed will be less likely to develop bed sores with a

water bed

A dam is thicker at the bottom than at the top mainly because

water pressure increases with depth

Which will remain the same for two identical books, one lying flat and the other standing on an end?

weight

What is the buoyant force that acts on a submerged object equal to?

The buoyant force is equal to the weight of the fluid displaced by the submerged object

How does the buoyant force on a submerged object compare with the weight of the water displaced?

The buoyant force is equal to the weight of the water displaced

Suppose you increase the depth of the object WITHOUT changing its height. What will happen to the force due to pressure on the bottom of the object?

The force due to pressure on the bottom of the object will increase

Suppose you increase the height of the object WITHOUT changing its depth under water. What will happen to the force due to pressure on the bottom of the object?

The force due to pressure on the bottom of the object will increase

Suppose you increase the height of the object WITHOUT changing its depth under water. What will happen to the net buoyant force?

The net buoyant force will increase

Suppose you increase the depth of the object WITHOUT changing its height. What will happen to the net buoyant force?

The net buoyant force will stay the same

What is the condition in which the buoyant force on an object does equal the weight of the object?

The object is neutrally buoyant, so it will neither sink nor float

What happens to the pressure in all parts of a confined fluid if the pressure in one part is increased?

The pressure everywhere increases by the same amount

How does pressure at the bottom of a body of water relate to the weight of water above each square meter of the bottom surface?

The pressure is the weight of the water divided by 1 m^2

Why does the buoyant force act upward on an object submerged in water?

The pressure upward on the deeper bottom is greater than the downward pressure on the top

If you swim beneath the surface in saltwater, will the pressure be greater than in fresh water at the same depth?

The pressure will be greater

How does the water pressure 1 m below the surface of a small pond compare with the water pressure 1 m below the surface of a huge lake?

The pressure will be the same

How does the volume of a completely submerged object compare with the volume of water displaced?

The volumes are equal

When Dr. Hewitt immerses an object in water the second time and catches the water that is displaced by the object, how does the weight lost by the object compare to the weight of the water displaced?

The weight loss of the object is equal to the weight of the water displaced

A mountain that floats on the mantle indicates that the density of the mantle is

greater than that of the mountain

Does the buoyant force on a submerged object depend on the volume of the object or on the weight of the object?

Volume

The attraction between like substances, stickiness, is called

cohesion

Surface tension is a direct result of

cohesive forces between molecules in a liquid

Surface tension of liquids

decreases as the liquid temperature increases

When you float in fresh water, the buoyant force that acts on you is equal to your weight. When you float higher in the denser water of the Dead Sea, the buoyant force that acts on you is

equal to your weight

While standing, your blood pressure is normally greatest in your

feet

The concept of pressure involves both

force and area