Test Answers on Test 1 Questions
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A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will a. rise to the surface. b. need more information c. remain where it is released. d. sink to the bottom.
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c. remain where it is released.
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Two cyclists who weigh the same and have identical bicycles ride up the same mountain, both starting at the same time. Joe rides straight up the mountain, and Bob rides up the longer road that has a lower grade. Joe gets to the top before Bob. Ignoring friction and wind resistance, which statement is true? a. The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob. b. Bob and Joe exerted the same amount of work, and the average power of each cyclist was also the same. c. The amount of work done by Joe is greater than the amount of work done by Bob, and the average power exerted by Joe is greater than that of Bob. d. The average power exerted by Bob and Joe was the same, but Joe exerted more work in getting there.
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a. The amount of work done by Joe is equal to the amount of work done by Bob, but the average power exerted by Joe is greater than that of Bob.
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A spherical ball of lead (density 11.3 g/cm3) is placed in a tub of mercury (density 13.6 g/cm3). Which answer best describes the result? a. The lead ball will float with about 83% of its volume above the surface of the mercury b. The lead will sink to the bottom of the mercury. c. The lead ball will float with its top exactly even with the surface of the mercury. d. Need more information. e. The lead ball will float with about 17% of its volume above the surface of the mercury.
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e. The lead ball will float with about 17% of its volume above the surface of the mercury.
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The Bernoulli effect is responsible for the lift force on an airplane wing. Wings must therefore be designed so as to insure that a. air molecules move more rapidly past the lower surface of the wing than past the upper surface b. air molecules move more rapidly past the upper surface of the wing than past the lower surface. c. air molecules will be deflected downward when they hit the wing. d. wings are thick enough to create a significant pressure difference between the top and bottom surfaces of the wings because of the different heights of these surfaces. e. air molecules will be deflected upward when they hit the wing.
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b. air molecules move more rapidly past the upper surface of the wing than past the lower surface.
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As the speed of a moving fluid increases, the pressure in the fluid a. remains constant. b. increases. c. decreases. d. may increase or decrease, depending on the density of the fluid.
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c. decreases.
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Which of the following situations is impossible? a. An object has zero velocity but non-zero acceleration. b. An object has velocity directed east and acceleration directed west. c. An object has constant non-zero velocity and changing acceleration. d. An object has constant non-zero acceleration and changing velocity.
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c. An object has constant non-zero velocity and changing acceleration.
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You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back toward your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to maximize your speed on the skateboard? a. catch the ball. b. your final speed on the skateboard will be the same regardless whether you catch the ball or deflect the ball. c. deflect the ball back. d. Need more information.
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c. deflect the ball back.
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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 slower, which makes the pressure lower than at the lower face. b. the air above the upper face of the paper moves faster, which makes the pressure higher than at the lower face. c. the air above the upper face of the paper moves slower, which makes the pressure higher than at the lower face. d. the air above the upper face of the paper moves faster, which makes the pressure lower than at the lower face.
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d. the air above the upper face of the paper moves faster, which makes the pressure lower than at the lower face.
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Consider two less-than-desirable options. In the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. In the second option you are driving 30 mph and crash head-on into a stationary brick wall. In neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. Which of these two situations would result in the greatest impact force? a. Hitting the other car. b. The force would be the same in both cases. c. We cannot answer this question without more information. d. Hitting the brick wall.
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b. The force would be the same in both cases.
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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. not change. b. decrease, but not by one-half. c. increase, but not double. d. double.
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a. not change.
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An object is moving to the right, and experiencing a net force that is directed to the right. The magnitude of the force is decreasing with time. The speed of the object is a. decreasing. b. need more information. c. constant in time. d. increasing.
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d. increasing.
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Three cars, car X, car Y, and car Z, begin accelerating from rest, at the same time. Car X is more massive than car Y, which is more massive than car Z. The net force exerted on each car is identical. After 10 seconds, which car has the most amount of momentum? a. They all have the same amount of momentum. b. Car Y c. Car Z d. Car X
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a. They all have the same amount of momentum.
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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. less than the volume of fresh water. b. greater than the volume of fresh water. c. it sinks in any case. d. the same as the volume of fresh water.
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a. less than the volume of fresh water.
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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. remains constant. c. is zero. d. decreases.
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b. remains constant.
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Consider what happens when you jump up in the air. Which of the following is the most accurate statement? a. When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air. b. You are able to spring up because the earth exerts a force upward on you which is stronger than the downward force you exert on the earth. c. It is the upward force exerted by the ground that pushes you up, but this force can never exceed your weight. d. Since the ground is stationary, it cannot exert the upward force necessary to propel you into the air. Instead, it is the internal forces of your muscles acting on your body itself which propels the body into the air.
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a. When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air.
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Consider a heavy and light person jumping together with the same-size parachutes from the same altitude. Who will reach the ground first? Answers: a. the light person b. the heavy person c. both will reach at the same time d. need more information
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b. the heavy person
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A runner starts from rest and accelerates forward at the beginning of a race. What force accelerates the runner forward? a. frictional force b. gravitational force c. normal force d. Jedi force
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a. frictional force
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Which of the following is not a vector quantity? a. mass b. force c. acceleration d. position
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a. mass
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If an object has constant, non-zero acceleration, which of the following statements is true? a. the momentum is changing b. the velocity is constant c. the sum of the forces is zero d. the position is constant
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a. the momentum is changing
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Which of the following statements about an object's mass is true? a. mass is equal to (net force)/acceleration b. mass is equal to weight c. mass is equal to momentum d. mass is equal to volume
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a. mass is equal to (net force)/acceleration (F = M*A)
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Acceleration and velocity are actually... a. the same b. rates, but for different quantities c. the same when direction is not a factor d. the same in the free-fall situations
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rates, but for different quantities
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You are sitting still in your chair thinking about this question. Which of the following statements is true? a. there is a gravitational force between you and your neighbor b. there are no forces acting on you c. your velocity is changing d. the sum of the forces acting on you is non-zero
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a. there is a gravitational force between you and your neighbor
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Neglecting air resistance, a brick and a feather are dropped from rest at the same height. Which of the following statements is true? a. their accelerations are equal b. their masses are equal c. the forces acting on them are equal d. their momenta are equal
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a. their accelerations are equal
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An automobile cannot maintain a constant velocity when a. accelerating b. rounding a curve c. both of the above d. neither of the above
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c. both of the above
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An automobile cannot maintain a constant speed when... a. rounding a curve b. accelerating c. both of the above d. neither of the above
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b. accelerating
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Which of the following is a conserved quantity? a. linear momentum b. position c. velocity d. acceleration
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a. linear momentum
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For which of the following statements is the total work done on an object non-zero? a. a force acts on the object and moves it some distance b. net forces acting on the object are zero c. the object does not move d. the object is moved some distance, then moved back to the original position
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a. a force acts on the object and moves it some distance
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The force of friction can occur... a. between sliding objects b. in air c. in water d. all of the above e. none of the above
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d. all of the above
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Which of the following statements is false about a ball with mass, m, falling towards the earth? (Neglect air resistance) a. the speed of the ball is constant b. the earth exerts a force downwards with magnitude mg on the ball c. the ball exerts a force upwards with magnitude mg on the earth d. the acceleration of the ball is constant
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a. the speed of the ball is constant
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A spacecraft lifts off thanks to ejecting a lot of combusted fuel fumes. This is an example of conservation of... a. linear momentum b. potential energy c. kinetic energy d. velocity
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a. linear momentum
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In which situation is a car accelerating? a. moving at 50 mph on a curve b. sitting at a red light c. moving at 50 mph, in a straight line d. moving at 50 mph, in a straight line, up a hill
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a. moving at 50 mph on a curve
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The atomic number of an element matches the number of... a. neutrons in a neutral atom b. protons in the nucleus of an atom c. electrons in an ionized atom d. neither of the above.
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b. protons in the nucleus of an atom
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Buoyancy
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- Apparent loss of weight of a submerged object. - Amount equals weight of liquid displaced (volume of object = volume of liquid displaced)
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Archimedes' Principle
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- An immersed body (completely or partially) is buoyed up by a force equal to the weight of the fluid it displaces - Buoyant force (F = weight displaced) vs. weight of object - Comes from Greek Scientist Archimedes
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Laminar Flow
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Smooth, steady flow of constant density fluid. (Turbulent = flow speed above critical point becomes chaotic)
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Bernoulli's Principle
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- Where the speed of a fluid increases, the internal pressure in the fluid decreases - Applies to a smooth, steady flow - Discovered by Daniel Bernoulli, 15th century Swiss Scientist
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Momentum
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- Property of moving things - Inertia in motion Momentum = Mass x Velocity
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Energy is...
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- A conserved quantity - Mover of substances - Property of a system that enables it to do work - Both a thing and a process - Observed when transferred or transformed
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Kinetic Energy
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Energy of motion. KE = (1/2) x Mass x Velocity^2
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Potential Energy
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Stored energy held in readiness with a potential for doing work. PE = Mass x Gravity x Height (equal to work done in lifting it)
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Work
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Force x Distance **Newton Meters (Nm) or Joules (J)
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Power
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Measure of how fast work is done. P = Work/Time **Watts (1J/s)
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Impulse
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Force x Time **Changes Momentum
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Pressure
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The force per unit area that one object exerts on another. Pa = Force x Area **Pascals (Pa) || N/m^2 || lb/ft^2
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Boyle's Law
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Pressure x Volume = [Constant] P1 x V1 = P2 x V2
