Q&A Hero

Q: An object floats on the surface of a fluid. For purposes of calculating the torque on it, the buoyant force is taken to act at: A) the center of the bottom surface of the object B) the center of gravity of the object C) the center of gravity of the fluid that the object replaced D) the geometric center of the object E) none of the above

Q: A block of wood weighs 160 N and has a specific gravity of 0.60. To sink it in fresh water requires an additional downward force of: A) 54 N B) 64 N C) 96 N D) 110 N E) 240 N

Q: A cork floats on the surface of an incompressible liquid in a container exposed to atmospheric pressure. The container is then sealed and the air above the liquid is evacuated. The cork: A) sinks slightly B) rises slightly C) floats at the same height D) bobs up and down about its old position E) behaves erratically

Q: A small steel ball floats in a half-full container of mercury. When water is added: A) the ball will float on the water B) the ball will rise slightly C) the mercury will float on the water D) the ball will sink to the bottom of the container E) the ball will lower slightly more into the mercury

Q: A pirate chest rests at the bottom of an ocean. If the water is still, the net force it exerts on the chest: A) is upward B) is downward C) is zero D) depends on the mass of the chest E) depends on the contents of the chest

Q: A block of ice at 0°C containing a piece of cork is floating on the surface of water in a beaker. When the ice has melted the water level:A) is higherB) is lowerC) is the sameD) depends on the initial ratio of water to iceE) depends on the shape of the ice block

Q: A block of ice at 0°C is floating on the surface of water in a beaker. The surface of the water just comes to the top of the beaker. When the ice melts the water level will:A) rise and overflow will occurB) remain the sameC) fallD) depend on the initial ratio of water to iceE) depend on the shape of the block of ice

Q: A certain object floats in fluids of density1) 0.9²02) ²03) 1.1²0Rank these fluids according to the volume displaced by the object, least to greatest.A) 1, 2, 3B) 3, 2, 1C) 2, 3, 1D) 3, 1, 2E) All are the same

Q: Two identical blocks of ice float in water as shown. Then: A) block A displaces a greater volume of water since the pressure acts on a smaller bottom area B) block B displaces a greater volume of water since the pressure is less on its bottom C) the two blocks displace equal volumes of water since they have the same weight D) block A displaces a greater volume of water since its submerged end is lower in the water E) block B displaces a greater volume of water since its submerged end has a greater area

Q: A certain object floats in fluids of density1) 0.9²02) ²03) 1.1²0Which of the following statements is true?A) the buoyant force of fluid 1 is greater than the buoyant forces of the other two fluidsB) the buoyant force of fluid 3 is greater than the buoyant forces of the other two fluidsC) the three fluids exert the same buoyant forceD) the object displace the same volume of all three fluidsE) none of these are true

Q: "An object completely submerged in a fluid displaces its own volume of fluid." This is: A) Pascal's paradox B) Archimedes' principle C) Pascal's principle D) true, but none of the above E) false

Q: A U-tube has dissimilar arms, one having twice the diameter of the other. It contains an incompressible fluid and is fitted with a sliding piston in each arm, with each piston in contact with the fluid. When an applied force does work Win pushing the piston in the narrow arm down, the fluid does work __________ on the piston in the wide arm. A) W B) 2W C) W/2 D) 4W E) W/4

Q: A U-tube has dissimilar arms, one having twice the diameter of the other. It contains an incompressible fluid and is fitted with a sliding piston in each arm, with each piston in contact with the fluid. When the piston in the narrow arm is pushed down a distance d, the piston in the wide arm rises a distance: A) d B) 2d C) d/2 D) 4d E) d/4

Q: The two arms of a U-tube are not identical, one having twice the diameter of the other. A cork in the narrow arm requires a force of 16 N to remove it. The tube is filled with water and the wide arm is fitted with a piston. The minimum force that must be applied to the piston to push the cork out is: A) 4 N B) 8 N C) 16 N D) 32 N E) 64 N

Q: A hydraulic press has one piston of diameter 2.0 cm and the other piston of diameter 8.0 cm. What force must be applied to the smaller piston to obtain a force of 1600 N at the larger piston: A) 100 N B) 400 N C) 1600 N D) 6400 N E) 26000 N

Q: One piston in a hydraulic lift has an area that is twice the area of the other. When the pressure at the smaller piston is increased by pthe pressure at the larger piston:A) increases by 2pB) increases by p/2C) increases by pD) increases by 4pE) does not change

Q: The hydraulic automobile jack illustrates: A) Archimedes' principle B) Pascal's principle C) Hooke's law D) Newton's third law E) Newton's second law

Q: Which of the following statements about Pascal's principle is true? A) It is valid only for incompressible fluids B) It explains why light objects float C) It explains why the pressure is greater at the bottom of a lake than at the surface D) It is valid only for objects that are less dense than water E) None of the above is true

Q: The principle of fluid pressure which is used in hydraulic brakes or lifts is that: A) pressure is the same at all levels in a fluid B) increases of pressure are transmitted equally to all parts of a fluid C) the pressure at a point in a fluid is due to the weight of the fluid above it D) increases of pressure can only be transmitted through fluids E) the pressure at a given depth is proportional to the depth in the fluid

Q: An open-tube manometer is used to measure the gauge pressure in a tank. If the manometer is filled with mercury, and the open end is at a height of 15 cm above the end attached to the tank, what is the gauge pressure in the tank? The density of mercury is 14 x 103kg/m3. A) 2.1 x 103Pa B) 2.1 x 104Pa C) 4.0 x 104Pa D) 1.2 x 105Pa E) 2.1 x 106Pa

Q: To measure moderately low pressures oil with a density of 8.5x102kg/m3is used in place of mercury in a barometer. A change in the oil column of 1.0 mm indicates a change in pressure of about:A) 1.2 x10-7PaB) 1.2 x10-5PaC) 0.85 PaD) 1.2 PaE) 8.3 Pa

Q: Barometers and open-tube manometers are two instruments that are used to measure pressure. Which statement is true? A) Both measure gauge pressure B) Both measure absolute pressure C) Barometers measure gauge pressure and manometers measure absolute pressure D) Barometers measure absolute pressure and manometers measure gauge pressure E) Both measure an average of the absolute and gauge pressures

Q: Mercury is a convenient liquid to use in a barometer because: A) it is a metal B) it has a high boiling point C) it expands little with temperature D) it has a high density E) it looks silvery

Q: To obtain the absolute pressure from the gauge pressure: A) subtract atmospheric pressure B) add atmospheric pressure C) subtract 273 D) add 273 E) convert to N/m2

Q: A long U-tube contains mercury (density = 14x103kg/m3). When 10 cm of water (density = 1.0 x103kg/m 3) is poured into the left arm, the mercury in the right arm rises above its original level by:A) 0.36 cmB) 0.72 cmC) 14 cmD) 35 cmE) 70 cm

Q: A uniform U-tube is partially filled with water. Oil, of density 0.75 g/cm3, is poured into the right arm until the water level in the left arm rises 3 cm. The length of the oil column is then: A) 2.25 cm B) 8 cm C) 6 cm D) 4 cm E) need to know the cross-sectional area of the U-tube

Q: The density of water is 1.0 g/cm3. If h= 20 cm,the density of the oil in the left column of the U-tube shown below is: A) 0.20 g/cm3 B) 0.90 g/cm3 C) 1.0 g/cm3 D) 1.3 g/cm3 E) 5.0 g/cm3

Q: The diagram shows a U-tube having cross-sectional area Aand partially filled with oil of density ². A solid cylinder, which fits the tube tightly but can slide without friction, is placed in the right arm. The system reaches equilibrium. The weight of the cylinder is:A) AL²gB) L3²gC) A²(L+ h)gD) A²(L- h)gE) none of these

Q: Several cans of different sizes and shapes are all filled with the same liquid to the same depth. Then: A) the weight of the liquid is the same for all cans B) the force of the liquid on the bottom of each can is the same C) the least pressure is at the bottom of the can with the largest bottom area D) the greatest pressure is at the bottom of the can with the largest bottom area E) the pressure on the bottom of each can is the same

Q: Which of the following five statements, concerning the upper surface pressure of a liquid, is FALSE? A) it is independent of the surface area B) it is the same for all points on that surface C) it would not increase if the liquid depth were increased D) it would increase if the liquid density were increased E) it would increase if the atmospheric pressure increased

Q: In a stationary homogeneous liquid: A) pressure is the same at all points B) pressure depends on the direction C) pressure is independent of any atmospheric pressure on the upper surface of the liquid D) pressure is the same at all points at the same level E) none of the above

Q: A closed hemispherical shell of radius Ris filled with fluid at uniform pressure p. The net force of the fluid on the curved portion of the shell is given by:A) 2R2pB) R2pC) 4R2pD) (4/3)R2pE) (4/3)R3p

Q: The vessels shown below all contain water to the same height. Rank them according to the pressure exerted by the water on the vessel bottoms, least to greatest. A) 1, 2, 3, 4 B) 3, 4, 2, 1 C) 1, 2, 4, 3 D) 2, 3, 4, 1 E) All pressures are the same

Q: A bucket of water is pushed from left to right with increasing speed across a horizontal surface. Consider the pressure at two points at the same level in the water. A) It is the same B) It is higher at the point on the left C) It is higher at the point on the right D) At first it is higher at the point on the left but as the bucket speeds up it is lower there E) At first it is higher at the point on the right but as the bucket speeds up it is lower there

Q: A bucket resting on the floor of an elevator contains an incompressible fluid of density ². When the elevator has a downward acceleration of magnitude athe pressure difference between two points in a fluid, separated by a vertical distance h, is given by:

Q: A bucket resting on the floor of an elevator contains an incompressible fluid of density ². When the elevator has an upward acceleration athe pressure difference between two points in a fluid separated by a vertical distance h, is given by:A) ²ahB) ²ghC) ²(g+ a)hD) ²(g -a)hE) ²gah

Q: An airtight box, having a lid of area 80.0 cm2, is partially evacuated. Atmospheric pressure is 1.01x105Pa. A force of 108 lb is required to pull the lid off the box. The pressure in the box was:A) 1.35 x104PaB) 2.60x104PaC) 4.10 x104PaD) 8.75 x104PaE) 1.36 x105Pa

Q: The pressure exerted on the ground by a man is greatest when: A) he stands with both feet flat on the ground B) he stands flat on one foot C) he stands on the toes of one foot D) he lies down on the ground E) all of the above yield the same pressure

Q: If pis a pressure and ²is a mass density then p/²has units of:A) m2B) m2/s2C) N/m2D) kg/m2E) m3/kg

Q: All fluids are: A) gases B) liquids C) gases or liquids D) non-metallic E) transparent

Q: 1 Pa is:A) 1 N/mB) 1 m/NC) 1 kg/m.sD) 1 kg/m.s2E) 1 N/m.s

Q: Gases may be distinguished from other forms of matter by their: A) lack of color B) small atomic weights C) inability to form free surfaces D) ability to flow E) ability to exert a buoyant force

Q: A planet is in circular orbit around the Sun. Its distance from the Sun is four times the average distance of Earth from the Sun. The period of this planet is: A) 4 Earth years B) 8 Earth years C) 16 Earth years D) 64 Earth years E) 2.5Earth years

Q: Planet 1 and planet 2 are both in circular orbits around the same central star. The orbit of planet 2 has a radius that is much larger than the radius of the orbit of planet 1. This means that: A) the period of planet 1 is greater than the period of planet 2 and the speed of planet 1 is greater than the speed of planet 2 B) the period of planet 1 is greater than the period of planet 2 and the speed of planet 1 is less than the speed of planet 2 C) the period of planet 1 is less than the period of planet 2 and the speed of planet 1 is less than the speed of planet 2 D) the period of planet 1 is less than the period of planet 2 and the speed of planet 1 is greater than the speed of planet 2 E) the planets have the same speed and the same period

Q: The orbit of a certain a satellite has a semimajor axis of 1.5 x107m and an eccentricity of 0.20. Its perigee (minimum distance) and apogee (maximum distance) are respectively:A) 1.2 x107m, 1.8 x107mB) 3.0 x106m, 1.2 x107mC) 6.0 x106m, 9.0 x106mD) 1.0 x107m, 1.2 x107mE) 9.6 x106m, 1.8 x107m

Q: The elliptical orbit of a planet around the Sun is shown on the diagram. Which of the following statements is true? A) the eccentricity of the orbit is less than zero B) the eccentricity of the orbit is greater than 1 C) the sun might be at point C D) the sun might be at point D E) the sun might be at point B

Q: In planetary motion the line from the star to the planet sweeps out equal areas in equal times. This is a direct consequence of: A) the conservation of energy B) the conservation of momentum C) the conservation of angular momentum D) the conservation of mass E) none of the above

Q: A small satellite is in elliptical orbit around Earth as shown. If Ldenotes the magnitude of its angular momentum and Kdenotes kinetic energy: A) L2>L1and K2>K1 B) L2>L1and K2= K1 C) L2= L1and K2= K1 D) L2<L1and K2= K1 E) L2= L1and K2>K1

Q: For a planet in orbit around a star the perihelion distance is rpand its speed at perihelion isvp. The aphelion distance israand its speed at aphelion is va. Which of following is true? A) va= vp B) va/ra= vp/rp C) vara= vprp D) va/ra2= vp/rp2 E) vara2= vprp2

Q: A planet travels in an elliptical orbit about a star as shown. At what pair of points is the speed of the planet the same? A) W and S B) P and T C) P and R D) Q and U E) Vand R

Q: The speed of a comet in an elliptical orbit about the sun: A) decreases while it is receding from the sun B) is constant C) is greatest when farthest from the sun D) varies sinusoidally with time E) equals L/(mr), where Lis its angular momentum, mis its mass, and ris its distance from the sun

Q: A planet travels in an elliptical orbit about a star X as shown. The magnitude of the acceleration of the planet is: A) greatest at point Q B) greatest at point S C) greatest at point U D) greatest at point W E) the same at all points

Q: Consider the statement: "Earth moves in a stable orbit around the Sun and is therefore in equilibrium". The statement is: A) false, because no moving body can be in equilibrium B) true, because the Earth does not fall into or fly away from the sun C) false, because the Earth is rotating on its axis and no rotating body can be in equilibrium D) false, because the Earth has a considerable acceleration E) true, because if it were not in equilibrium then buildings and structures would not be stable

Q: Neglecting air resistance, the escape speed from a certain planet for an empty space vehicle is 1.12 ï‚´104m/s. What is the corresponding escape speed for the fully loaded vehicle which has triple the mass of the empty one?A) 3.73x103m/sB) 1.12 x104m/sC) 3.36 x104m/sD) 1.01x105m/sE) 1.40x1012m/s

Q: Neglecting air resistance, a 1.0-kg projectile has an escape velocity of about 11 km/s at the surface of Earth. The corresponding escape velocity for a 2.0 kg projectile is: A) 5.5 km/s B) 7.8 km/s C) 11 km/s D) 16 km/s E) 22 km/s

Q: The escape velocity at the surface of Earth is approximately 11 km/s. What is the mass, in units of ME(the mass of the Earth), of a planet with twice the radius of Earth for which the escape speed is twice that for Earth? A) 2ME B) 4ME C) 8ME D) 1/2ME E) 1/4ME

Q: In order to fire a projectile upward and have it escape the Earth's gravity, A) the kinetic energy of the projectile may have any positive value. B) the potential energy of the projectile must be positive C) the total energy (kinetic plus potential) of the projectile must be negative D) the total energy (kinetic plus potential) of the projectile must not be negative E) the total energy (kinetic plus potential) of the projectile must be exactly zero

Q: To measure the mass of a planet with the same radius as Earth, an astronaut drops an object from rest (relative to the planet) from an altitude of one radius above the surface. When the object hits its speed is 4 times what it would be if the same experiment were carried out for Earth. In units of ME(the mass of the Earth), the mass of the planet is: A) 2 ME B) 4 ME C) 8 ME D) 16 ME E) 32 ME

Q: A projectile is fired straight upward from Earth's surface with a speed that is half the escape speed. If Ris the radius of Earth, the highest altitude reached, measured from the surface, is: A) R/4 B) R/3 C) R/2 D) R E) 2R

Q: An object is dropped from an altitude of one Earth radius above Earth's surface. If Mis the mass of Earth and Ris its radius, the speed of the object just before it hits Earth, neglecting air resistance, is given by: A) B) C) D) E)

Q: An artificial Earth satellite of mass mis moved from a circular orbit with radius Rto a circular orbit with radius 2R. If the mass of the Earth is ME, the work done by the gravitational force is:A) zeroB) GMEm/RC) GMEm/2RD) -GMEm/RE) -GMEm/2R

Q: An artificial Earth satellite is moved from a circular orbit with radius Rto a circular orbit with radius 2R. During this move: A) The gravitational force does no work. B) The gravitational force does positive work. C) The gravitational force does negative work. D) The work done by the gravitational force cannot be determined without knowing the path of the satellite. E) The work done by the gravitational force cannot be determined without knowing what force caused the satellite to change its orbit.

Q: Two particles, each of mass m, are a distance dapart. To bring a third particle, with mass 2m, from far away to a resting point midway between the two particles,an external agent must do work equal to:A) 4Gm2/dB) -4Gm2/dC) 8Gm2/dD) -8Gm2/dE) zero

Q: Each of the four corners of a square with edge ais occupied by a point mass m. There is a fifth mass, also m, at the center of the square. To remove the mass from the center to a point far away the work that must be done by an external agent is given by:A) 4Gm2/aB) -4Gm2/aC) D) E) 4Gm2/a2

Q: A spherical shell has inner radius R1, outer radius R2, and mass M, distributed uniformly throughout the shell. The magnitude of the gravitational force exerted on the shell by a point particle of mass m, located a distance dfrom the center, outside the inner radius and inside the outer radius, is: A) 0 B) GMm/d2 C) D) E)

Q: The mass density of a certain planet has spherical symmetry but varies in such a way that the mass inside every spherical surface with center at the center of the planet is proportional to the radius of the surface. If ris the distance from the center of the planet to a point mass inside the planet, the gravitational force on the mass is: A) not dependent on r B) proportional to r2 C) proportional to r D) proportional to 1/r E) proportional to 1/r2

Q: Of the following where would the weight of an object be the least? A) 2000 miles above Earth's surface B) At the north pole C) At the equator D) At the center of Earth E) At the south pole

Q: A spring scale, calibrated in newtons, is used to weigh sugar. If it were possible to weigh sugar at the following locations, where will the buyer get the most sugar to a newton? A) At the north pole B) At the equator C) Near the center of Earth D) On the Moon E) On Jupiter

Q: A particle might be placed 1) inside a uniform spherical shell of mass M, but not at the center 2) inside a uniform spherical shell of mass M, at the center 3) outside a uniform spherical shell of mass M, a distance rfrom the center 4) outside a uniform solid sphere of mass M, a distance 2rfrom the center Rank these situations according to the magnitude of the gravitational force on the particle, least to greatest. A) All tie B) 1, 2, 3, 4 C) 1 and 2 tie, then 3 and 4 tie D) 1 and 2 tie, then 3, then 4 E) 1 and 2 tie, then 4, then 3

Q: A spherical shell has inner radius R1, outer radius R2, and mass M, distributed uniformly throughout the shell. The magnitude of the gravitational force exerted on the shell by a point mass ma distance dfrom the center, inside the inner radius, is: A) 0 B) C) GMm/d2 D) E) GMm/(R1" d)2

Q: An astronaut in an orbiting space-craft feels "weightless" because she: A) is beyond the range of gravity B) is pulled outwards by centrifugal force C) has no acceleration D) has the same acceleration as the space-craft E) is outside Earth's atmosphere

Q: A rocket ship is coasting toward a planet. Its captain wishes to know the value of gat the surface of the planet. This may be inferred by: A) measuring the apparent weight of one of the crew B) measuring the apparent weight of an object of known mass in the ship C) measuring the diameter of the planet D) measuring the density of the planet E) observing the ship's acceleration and correcting for the distance from the center of the planet

Q: The mass of a hypothetical planet is 1/100 that of Earth and its radius is 1/4 that of Earth. If a person weighs 600 N on Earth, what would he weigh on this planet? A) 24 N B) 48 N C) 96 N D) 192 N E) 600 N

Q: Mars has a mass of about 0.1075 times the mass of Earth and a diameter of about 0.533 times the diameter of Earth. The acceleration of a body falling near the surface of Mars is about: A) 0.30 m/s2 B) 1.4 m/s2 C) 2.0 m/s2 D) 3.7 m/s2 E) 26 m/s2

Q: If Earth were to rotate only 100 times per year about its axis: A) airplanes flying west to east would make better time B) we would fly off Earth's surface C) our apparent weight would slightly increase D) Earth's atmosphere would float into outer space E) our apparent weight would slightly decrease

Q: Suppose you have a pendulum clock which keeps correct time on Earth (acceleration due to gravity = 9.8 m/s2). Without changing the clock, you take it to the Moon (acceleration due to gravity = 1.6 m/s2). For every hour interval (on Earth) the Moon clock will record: A) (9.8/1.6) h B) 1 h C) h D) (1.6/9.8) h E) h

Q: An astronaut finishes some work on the outside of his satellite, which is in circular orbit around the Earth. He leaves his wrench outside the satellite. If there is no air resistance, the wrench will: A) fall directly down to the Earth B) continue in orbit at reduced speed C) continue in orbit with the satellite D) fly off tangentially into space E) spiral down to the Earth

Q: An artificial satellite of the Earth releases a bomb. Neglecting air resistance, the bomb will: A) strike Earth under the satellite at the instant of release B) strike Earth under the satellite at the instant of impact C) strike Earth ahead of the satellite at the instant of impact D) strike Earth behind the satellite at the instant of impact E) never strike Earth

Q: A mass mis located at the origin; a second mass mis at x= d. A third mass mis above the first two so the three masses form an equilateral triangle. What is the net gravitational force on the third mass? A) 2Gm2/d2 B) Gm2/d2 C) Gm2/d2 D) Gm2/2d2 E) Gm2/2d2

Q: The approximate value of gat an altitude above Earth equal to one Earth diameter is: A) 9.8 m/s2 B) 4.9 m/s2 C) 2.5 m/s2 D) 1.9 m/s2 E) 1.1 m/s2