1.1 Quiz

A physics teacher gives a solid object to each student in her class. The objects are each made of the same material but have different shapes and sizes. The teacher asks the students to measure the mass and volume of their object and to work together to determine the density of the material from which the objects are made. Which of the following methods will give the best estimate of the material's density?

Each student shares the mass and volume of their object with the class. The class then creates a graph plotting mass as a function of volume, draws a best-fit line through the data, and uses the slope of the best-fit line as the density of the material.

In an experiment, a student releases an object from rest in four different liquids and observes whether it floats. The results are listed in the table. Which of the following is true about the density of the object?

It is between the density of distilled water and the density of salt water.

A sphere made of gold is moving downward through liquid mercury at an increasing speed. The mercury exerts a net buoyant force in the upward direction on the gold sphere. Which of the following describes a Newton's-third-law pair for this force?

The gold sphere exerts a force on the mercury with magnitude equal to the buoyant force.

Water is poured into a U-shaped tube and allowed to come to rest, as shown in the figure. Which of the following can help explain why the water in the left and right sides of the tube reaches the same height? Select two answers.

The weight of water in the left and right halves of the tube is the same. The force exerted by the atmosphere on the surface of the water is the same on both sides.

In an experiment, a student puts each of three objects, A, B, and C, in four different liquids and observes whether the objects float. The results are listed in the table. Which columns contain information that is most useful for estimating the density of object C?

Oil and Gasoline

The figure shows a block of wood floating in a beaker of water. Which of the following is true of the force exerted by the wood on the water?

The wood exerts a downward force on the water that is equal in magnitude to the weight of the wood.

A student wants to determine whether the density of a solid cube of copper will decrease as its temperature is increased without melting the cube. Graphing which of the following will allow the student to study this question?

Volume as a function of temperature

A cube submerged in a rectangular tank of liquid is at rest. Which of the following is a Newton's third law pair of forces in this situation?

The force that the liquid exerts on a side of the tank and the force the side of the tank exerts on the liquid

A wooden cube is floating at rest on the surface of a liquid. Which of the following is an action-reaction pair of forces that can explain why the force exerted by the liquid on the bottom of the container is greater with the floating cube than without it?

The liquid exerts a net upward force on the cube, and the cube exerts a contact force on the liquid.

A sphere of mass 0.5kg is dropped into a column of oil. At the instant the sphere becomes completely submerged in the oil, the sphere is moving downward at 8m/s, the buoyancy force on the sphere is 4.0N, and the fluid frictional force is 4.0N. Which of the following describes the motion of the sphere at this instant?

The sphere's speed is decreasing while the sphere continues to move downward.

A block of weight W is floating in water, and one-third of the block is above the surface of the water. Which of the following correctly describes the magnitude F of the force that the block exerts on the water and explains why F has that value?

F=WF=W. The block is at rest, so the net force on it must be zero. The water must exert an upward force of magnitude FF on the block to make this so. The block then exerts a force of equal magnitude on the water.

Students are investigating the change in the density of water as the temperature of the water increases. The students measure the mass and the volume of a quantity of water and then heat the water to various temperatures in the range using a thermometer to measure the temperature. They then attempt to determine the density of the water at the different temperatures. Assume any changes of equipment or measuring tools due to temperature changes are negligible. Which of the following methods would allow the students to obtain data from which they could determine the change in density of the water at different temperatures?

Record the temperature of the water and precise measurements of the volume of the water.

A block of mass M is floating in a container of liquid and is partially submerged. The block is then replaced by a block of mass 2M. Which of the following describes two forces that are a Newton's-third-law force pair whose magnitudes are the same for the two situations?

The gravitational force Earth exerts on the liquid and the gravitational force the liquid exerts on Earth

A submarine of mass 3.6×106kg is submerged in water and at equilibrium. Inside of the submarine are ballast tanks filled with water. Some of the water in the ballast tanks is then ejected, decreasing the density of the submarine. The free-body diagram in the figure shows the magnitude and direction of the forces acting on the submarine after the water is ejected. The acceleration of the submarine is most nearly

1.1m/s21.1m/s2