physics exam 3

An element is a substance consisting of a.atoms of the same kind. b.atoms or molecules of the same kind. c.only protons. d.protons and electrons in balance.

A

Atoms in a crystal are held together by a.electrical bonding forces. b.nuclear forces. c.an absence of Brownian motion. d.a sort of atomic "glue."

A

Four small spheres of mercury coalesce to form a single sphere. Compared with the combined surface area of the smaller spheres, the surface of the big sphere is a.less. b.more. c.the same. d.None of the above.

A

If a hole is punched in the side or bottom of a boat, water spurting in will be a.perpendicular to the surface of the boat interior. b.in an upward direction. c.in such a way as to minimize flow rate. d.conserved.

A

If you add or subtract a proton to or from the nucleus of an atom, you produce a.a completely different atom. b.an isotope of the same atom. c.an ion. d.None of the above.

A

Liquid pumps operate due to differences in a.pressure. b.densities of fluids. c.viscosities of fluids. d.energies.

A

Molecules are composed of a.atoms. b.electrons and protons. c.atomic nuclei and orbiting electrons. d.particles larger than atoms.

A

The atomic number of an atom is defined in terms of its number of a.protons. b.neutrons. c.protons and neutrons. d.protons, neutrons, and electrons.

A

When you squeeze an air-filled party balloon you reduce its a.volume. b.mass. c.weight. d.All of these.

A

When you float in saltwater rather than in freshwater, the volume of water displaced is a.less and the buoyant force is unchanged. b.less and the buoyant force is more. c.unchanged and buoyant force is also unchanged. d.None of these.

A Explanation: Although the volume of water displaced is less, its weight equals your weight. Therefore, buoyant force is unchanged.

The crystals that make up minerals are composed of a.atoms with a definite geometrical arrangement. b.molecules that perpetually move. c.X-ray patterns. three-dimensional chessboards

A Explanation: Not all crystals are arranged like three-dimensional chessboards.

An old-fashioned farm water pump would work best a.in low-lying regions. b.in mountainous regions. c.if on the Moon. d.on freezing cold-days.

A Explanation: Such pumps operate by way of atmospheric pressure and are therefore best suited to low-lying regions where atmospheric pressure is greater.

An elastic material is one in which a.stretch is achieved for relatively small forces. b.original shape is restored when a deforming force is removed. c.when dropped, bouncing to practically the same height is achieved. d.internal tensions are relatively small.

B

Atmospheric pressure is caused by the atmosphere's a.density. b.weight. c.temperature. d.response to solar energy.

B

If a hot-air balloon hovers at a fixed altitude, the net weight of the balloon must be a.slightly less than the weight of displaced air. b.equal to the weight of displaced air. c.slightly greater than the weight of displaced air. d.None of these.

B

If air speed is greater along the top surface of a bird's wings, pressure of the moving air there is a.unaffected. b.less. c.more. d.turbulent.

B

Isotopes of a given element differ in a.atomic number. b.mass number. c.electron number. d.their place in the periodic table.

B

Opposite flanges in a properly positioned horizontal I-beam supported at each end undergo a.tension in the top and compression in the bottom flange. b.compression in the top and tension in the bottom flange. c.both compression and tension in both top and bottom flanges. d.compression only in both top and bottom.

B

Sarah lies on a bed of sharp nails. The pressure of each nail against her body is less with a.fewer nails. b.more nails. c.whatever number of nails, considering each nail. d.None of the above.

B

The buoyant force that acts on a 20,000-N ship is a.somewhat less than 20,000 N. b.20,000 N. c.more than 20,000 N. d.dependent on whether it floats in saltwater or in freshwater.

B

The classic periodic table a.has four legs. b.lists the known elements. c.is now outmoded and has been replaced by modeling programs. d.None of the above.

B

The reason you don't fall between the atoms in the floor you stand on involves a.the small spaces between atoms. b.electrical forces. c.the rigidity of solids. d.pressure.

B

The size of an atom is mostly determined by the space occupied by its a.nucleus. b.electrons. c.protons. d.neutrons.

B

The strength of a stone arch is due to a.tension between adjacent stones. b.compression between adjacent stones. c.Both of these. d.None of these.

B

When you sit in the middle of a horizontal bench supported at its ends, the top side of the bench is a.under tension and the bottom side under compression. b.compressed and the bottom is stretched. c.compressed and the neutral region in between is compressed. d.All of these.

B

When you stand on tiptoes on a bathroom scale, there is an increase in a.weight reading. b.pressure on the scale, not registered as weight. c.both weight and pressure on the scale. d.None of these.

B

The geometrical shape that has the smallest surface area compared with volume is the a.circle. b.sphere. c.cube. d.tetrahedron.

B Explanation: Hence water drops pull together due to surface tension and tend to form spheres.

Consider two tubes filled with water at the same height, one with freshwater and the other with saltwater. The pressure is greater at the bottom of the tube with a.freshwater. b.saltwater. c.Both the same. d.Depends on whether the tubes have the same cross-sectional area.

B Explanation: Saltwater is more dense than freshwater. Water pressure depends on depth and density.

As water in a confined pipe speeds up, the pressure it exerts against the inner walls of the pipe a.increases. b.decreases. c.remains constant if flow rate is constant. d.None of these.

B Explanation: Straight Bernoulli!

When a 20,000-N ship passes from saltwater into freshwater, buoyant force on the ship a.decreases. b.remains unchanged. c.increases. d.None of these.

B Explanation: The ship floats a bit lower in freshwater but will still displace the same weight of water.

Atoms combine to form molecules by way of a.nuclear forces. b.electric repulsion. c.shared or exchanged electrons. d.neutron attractions.

C

Considering Pascal's Principle, I apply a force to a fluid enclosed in a tube. The area of the output side of the tube is 20 times larger than the area of the input side of the tube. How does the output force compare to the input force? a.20 times smaller b.The same c.20 times larger d.None of the above

C

Surface tension in water is due to a.viscosity. b.density. c.adhesive forces. d.cohesive forces.

C

The atoms in isotopes of a particular element have different numbers of a.electrons. b.protons. c.neutrons. d.electric charges.

C

The higher one goes in the atmosphere, the less the a.atmospheric pressure. b.density of air. c.Both of these. d.None of these.

C

Water pressure at the bottom of a lake depends on the a.weight of water in the lake. b.surface area of the lake. c.depth of the lake. d.All of these.

C

Brownian motion has to do with the a.size of atoms. b.vibrations of atoms. c.random motions of atoms and molecules. d.rhythmic movements of Brownians.

C Comment: It was Einstein's investigation of Brownian motion that in 1922 won him the Nobel Prize in Physics.

A barometer can be used to measure a.atmospheric pressure. b.altitude. c.Both of these. d.None of these.

C Explanation: A barometer used to measure altitude is called an aneroid barometer.

According to Hooke's law, if you hang by a tree branch and note how much it bends, then hanging with twice the weight normally produces a.half the bend. b.the same bend. c.twice the bend. d.four times the bend.

C Explanation: F ~ ∆x; so twice the F means twice the ∆x.

The buoyant force that normally acts on a fish in water is a.slightly less than its weight. b.slightly more than its weight. c.equal to its weight. d.dependent on the depth of the fish.

C Explanation: Interestingly, however deep a fish swims, it nevertheless displaces a weight of water that matches its own weight.

A pair of vertical springs, side-by-side, equally support a 20-N load. If the load is doubled and the elastic limit of the springs is not reached, then the tension in each spring will be a.10 N. b.15 N. c.20 N. d.40 N.

C Explanation: Tension in each spring supporting the 20-N load will be 10 N. Doubling the load doubles each tension to 20 N.

A pail of water, brimful, weighs W, as noted on a weighing scale upon which it rests. A toy boat of weight w is placed in it. Water spills to accommodate the floating boat, keeping the pail brim full. The reading on the weighing scale is then a.W + w. b.W - w. c.W. d.None of these.

C Explanation: This is shown in Figure 13.18 and is the physics behind the famous Falkirk Wheel in Scotland!

When you squeeze an air-filled party balloon you increase its a.volume. b.mass. c.weight. d.density.

D

Which of these elements has atoms of the greatest mass? a.Helium b.Carbon c.Gold d.Uranium

D

Which of these elements has atoms with the greatest number of electrons? a.Helium b.Carbon c.Gold d.Uranium

D

Which of these has the greatest density? a.10 kg of concrete b.2 kg of concrete c.3 kg of iron d.1 g of lead

D

The main difference between hot gases and a plasma involves a.interatomic spacing. b.fluid pressure. c.minute quantities of antimatter. d.electrical conduction.

D Explanation: A property of a plasma is that it can conduct electricity.

Which of the following has the smallest mass? a.Proton b.Neutron c.Electron d.Except for slight differences, all have about the same mass.

c