physics class
A 10-kg box sitting on a horizontal surface is pulled by a 5.0-N force. A 3.0-N friction force retards the motion. What is the acceleration of the object? A) 0.20 m/s2 B) 0.30 m/s2 C) 0.50 m/s2 D) 5.0 m/s2
A
A 30.0-N stone is dropped from a height of 10.0 m, and strikes the ground with a velocity of 7.00 m/s. What average force of air friction acts on it as it falls? A) 22.5 N B) 75.0 N C) 225 N D) 293 N
A
A 4.00-kg box of fruit slides 8.0 m down a ramp, inclined at 30.0e from the horizontal. If the box slides at a constant velocity of 5.00 m/s, what is the work done by the weight of the box? A) 157 J B) -157 J + 78.4 J C) 78.4 J D) -78.4 J
A
A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the 5500 N force? A) 2.75 x 10^5 J B) 2975 kJ C) 30 J D) -5.20 X 10^5 J
A
A ball is thrown with a velocity of 20 m/s at an angle of 60e above the horizontal. What is the horizontal component of its instantaneous velocity at the exact top of its trajectory? A) 10 m/s B) 17 m/s C) 20 m/s D) zero
A
A bulldozer drags a log weighing 500 N along a rough surface. The cable attached to the log makes an angle of 30.0 with the ground. The coefficient of static friction between the log and the ground is 0.500. What minimum tension is required in the cable in order for the log to begin to move? A) 224 N B) 268 N C) 289 N D) 500 N
A
A net force F acts on a mass m and produces an acceleration a. What acceleration results if a net force 2F acts on mass 4m? A) a/2 B) 8a C) 4a D) 2a
A
A soccer ball is kicked with a velocity of 25 m/s at an angle of 45e above the horizontal. What is the vertical component of its acceleration as it travels along its trajectory? A) 9.80 m/s2 downward B) (9.80 m/s2) ˛ sin (45e) downward C) (9.80 m/s2) ˛ sin (45e) upward D) (9.80 m/s2) upward
A
A swimmer heading directly across a river 200 m wide reaches the opposite bank in 6 min 40 s. She is swept downstream 480 m. How fast can she swim in still water? A) 0.50 m/s B) 1.2 m/s C) 1.4 m/s D) 1.8 m/s
A
A wooden block slides directly down an inclined plane, at a constant velocity of 6.0 m/s. What is the coefficient of kinetic friction, if the plane makes an angle of 25e with the horizontal? A) 0.47 B) 0.42 C) 0.37 D) 0.91
A
An object is on a frictionless inclined plane. The plane is inclined at an angle of 30e with the horizontal. What is the object's acceleration? A) 0.50 g B) 0.56 g C) 0.87 g D) 1.0 g
A
An object is thrown upward with a speed of 12 m/s on the surface of planet X where the acceleration due to gravity is 1.5 m/s2. How long does it take for the object to reach the maximum height? A) 8.0 s B) 11 s C) 14 s D) 16 s
A
An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving upward, but slowing down. What is the tension in the string? A) less than mg B) exactly mg C) greater than mg D) zero
A
An object slides on a level surface in the +x direction. It slows and comes to a stop with a constant acceleration of -2.45 m/s2. What is the coefficient of kinetic friction between the object and the floor? A) 0.25 B) 0.50 C) 4.9 D) Impossible to determine without knowing the mass of the object.
A
If the net work done on an object is negative, then the object's kinetic energy A) decreases. B) remains the same. C) increases. D) is zero.
A
If the velocity versus time graph of an object is a horizontal line, the object is A) moving with constant non-zero speed. B) moving with constant non-zero acceleration. C) at rest. D) moving with infinite speed.
A
Of the following, which is not a unit of power? A) watt/second B) newton-meter/second C) joule/second D) watt
A
The area under the curve, on a Force versus position (F vs. x) graph, represents A) work. B) kinetic energy. C) power. D) potential energy.
A
The coefficient of static and kinetic frictions between a 3.0-kg box and a desk are 0.40 and 0.30, respectively. What is the net force on the box when a 15 N horizontal force is applied to the box? A) 6.2 N B) 12 N C) 8.8 N D) zero
A
Three forces, each having a magnitude of 30 N, pull on an object in directions that are 120e apart from each other. Make a statement concerning the resultant force. A) The resultant force is zero. B) The resultant force is greater than 30 N. C) The resultant force is equal to 30 N. D) The resultant force is less than 30 N.
A
When you sit on a chair, the resultant force on you is A) zero. B) up. C) down. D) depending on your weight.
A
Which of Newton's laws best explains why motorists should buckle-up? A) the first law B) the second law C) the third law D) the law of gravitation
A
An antitank weapon fires a 3.00-kg rocket which acquires a speed of 50.0 m/s after traveling 90.0 cm down a launching tube. Assuming the rocket was accelerated uniformly, what is the average force acted on it? A) 103 N B)˛ 103 N C˛ 103 N D)˛ 103 N
A mass X avg Velocity
Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the distance between them A) increases. B) remains constant. C) decreases. D) cannot be determined from the information given.
Answer: A
A cyclist does work at the rate of 500 W while riding. How much force does her foot push with when she is traveling at 8.0 m/s? A) 31 N B) 63 N C) 80 N D) 4000 N
Answer: B
A 100-N force has a horizontal component of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest, and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy? A) 200 J B) 160 J C) 120 J D) zero
B
A 30-N box is pulled 6.0 m up along a 37degree inclined plane. What is the work done by the weight (gravitational force) of the box? A) -11 J B) -1.1 X 10^2 J C) -1.4 X 10^2 J D) -1.8 X 10^2 J
B
A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the work done by the weight of the elevator? A) 2.75 X 10^5 J B) -2.45 X 10^5 J C) 3 X 10^4 J D) -5.20 X 10^5 J
B
A 60-kg skier starts from rest from the top of a 50-m high slope. What is the speed of the slier on reaching the bottom of the slope? (Neglect friction.) A) 22 m/s B) 31 m/s C) 9.8 m/s D) 41 m/s
B
A ball is thrown straight up with a speed of 36.0 m/s. How long does it take to return to its starting point? A) 3.67 s B) 7.35 s C) 11.0 s D) 14.7 s
B
A golf club hits a golf ball with a force of 2400 N. The golf ball hits the club with a force A) slightly less than 2400 N. B) exactly 2400 N. C) slightly more than 2400 N. D) close to 0 N.
B
A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final kinetic energy of the cart? A) 1030 J B) 2200 J C) 103 J D) 220 J
B
A horizontal force of 5.0 N accelerates a 4.0-kg mass, from rest, at a rate of 0.50 m/s2 in the positive direction. What friction force acts on the mass? A) 2.0 N B) 3.0 N C) 4.0 N D) 5.0 N
B
Action-reaction forces are A) equal in magnitude and point in the same direction. B) equal in magnitude but point in opposite directions. C) unequal in magnitude but point in the same direction. D) unequal in magnitude and point in opposite directions
B
An airplane with a speed of 120 km/h is headed 30.0e east of north in a wind blowing due west at 30.0 km/h. What is the speed of the plane relative to the ground? A) 90.0 km/h B) 110 km/h C) 137 km/h D) 150 km/h
B
An object is lifted vertically 2.0 m and held there. If the object weighs 90 N, how much work was done in lifting it? A) 360 J B) 180 J C) 90 J D) 0 J
B
An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving up at constant speed. What is the tension in the string? A) less than mg B) exactly mg C) greater than mg D) cannot be determined without knowing the speed
B
An object sits on a frictionless surface. A 16-N force is applied to the object, and it accelerates at 2.0 m/s2. What is the mass of the object? A) 4.0 kg B) 8.0 kg C) 32 kg D) 78 N
B
Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. As time progresses, the difference in their speeds A) increases. B) remains constant. C) decreases. D) cannot be determined from the information given.
B
During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the ice before it stops. What is the coefficient of kinetic friction between the puck and the ice? A) 0.090 B) 0.10 C) 0.11 D) 0.12
B
Human reaction time is usually greater than 0.10 s. If your friend holds a ruler between your fingers and releases it without warning, how far can you expect the ruler to fall before you catch it? A) at least 3.0 cm B) at least 4.9 cm C) at least 6.8 cm D) at least 9.8 cm
B
In the Atwood machine shown in Fig. 4-1, if M = 0.60 kg and m = 0.40 kg, what is the tension in the string? (Ignore friction and the mass of the pulley.) A) 3.1 N B) 4.7 N C) 7.1 N D) 7.5 N
B
On a calm day (no wind), you can run a 1500-m race at a velocity of 4.0 m/s. If you ran the same race on a day when you had a constant headwind which slows your speed by 2.0 m/s, the time it would take you to finish would be A) 250 s. B) 750 s. C) 1125 s. D) 9000 s.
B
The area under a curve in an acceleration versus time graph gives A) acceleration. B) velocity. C) displacement. D) position.
B
The driver of a motorboat that can move at 10 m/s in still water wishes to travel directly across a narrow strait in which the current flows at 5.0 m/s. At what angle upstream should the driver head the boat? A) 27e B) 30e C) 60e D) 63e
B
The quantity mgy is A) the kinetic energy of the object. B) the gravitational potential energy of the object. C) the work done on the object by the force. D) the power supplied to the object by the force.
B
The slope of a position versus time graph gives A) position. B) velocity. C) acceleration. D) displacement.
B
Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. When these two vectors are added, the magnitude of the sum A) is 2.0 m. B) could be as small as 2.0 m, or as large as 12 m. C) is 12 m. D) is larger than 12 m.
B
Which one of the following is an example of a vector quantity? A) distance B) velocity C) mass D) area
B
You lift a 10-N physics book up in the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the weight of the book? A) +10 J B) -10 J C) +5.0 J D) -5.0 J
B
A 15.0-kg object is moved from a height of 7.00 m above a floor to a height of 15.0 m above the floor. What is the change in gravitational potential energy? A) zero B) 1030 J C) 1176 J D) 1910 J
C
A 500-kg elevator is pulled upward with a constant force of 5500 N for a distance of 50.0 m. What is the net work done on the elevator? A) 2.75 X 10^5 J B) -2.45 X 10^5 J C) 3.00 X 10^4 J D) -5.20 X 10^5 J
C
A 60-kg skier starts from rest from the top of a 50-m high slope. If the work done by friction is - 6.0 ˛ 103 J, what is the speed of the skier on reaching the bottom of the slope? A) 17 m/s B) 24 m/s C) 34 m/s D) 31 m/s
C
A ball drops some distance and loses 30 J of gravitational potential energy. Do not ignore air resistance. How much kinetic energy did the ball gain? A) more than 30 J B) exactly 30 J C) less than 30 J D) cannot be determined from the information given
C
A ball falls from the top of a building, through the air (air friction is present), to the ground below. How does the kinetic energy (K) just before striking the ground compare to the potential energy (U) at the top of the building? A) K is equal to U. B) K is greater than U. C) K is less than U. D) It is impossible to tell.
C
A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown? A) 6.1 m/s B) 7.4 m/s C) 8.1 m/s D) 8.9 m/s
C
A block of mass M slides down a frictionless plane inclined at an angle q with the horizontal. The normal reaction force exerted by the plane on the block is A) Mg. B) Mg sin q. C) Mg cos q. D) zero, since the plane is frictionless.
C
A bullet is fired horizontally, and at the same instant a second bullet is dropped from the same height. Ignore air resistance. Compare the times of fall of the two bullets. A) The fired bullet hits first. B) The dropped bullet hits first. C) They hit at the same time. D) cannot tell without knowing the masses
C
A jet fighter plane is launched from a catapult on an aircraft carrier. It reaches a speed of 42 m/s at the end of the catapult, and this requires 2.0 s. Assuming the acceleration is constant, what is the length of the catapult? A) 16 m B) 24 m C) 42 m D) 84 m
C
A jumper in the long-jump goes into the jump with a speed of 12 m/s at an angle of 20e above the horizontal. How long is the jumper in the air before returning to the Earth? A) 0.21 s B) 0.42 s C) 0.84 s D) 1.3 s
C
A projectile of mass m leaves the ground with a kinetic energy of 220 J. At the highest point in its trajectory, its kinetic energy is 120 J. To what vertical height, relative to its launch point, did it rise? A) 220/(mg) meters B) 120/(mg) meters C) 100/(mg) meters D) Impossible to determine without knowing the angle of launch
C
A student pulls a box of books on a smooth horizontal floor with a force of 100 N in a direction of 37.0e above the horizontal. If the mass of the box and the books is 40.0 kg, what is the normal force on the box? A) 292 N B) 312 N C) 332 N D) 392 N
C
A student pulls a box of books on a smooth horizontal floor with a force of 100 N in a direction of 37e above the horizontal. If the mass of the box and the books is 40.0 kg, what is the acceleration of the box? A) 1.5 m/s2 B) 1.9 m/s2 C) 2.0 m/s2 D) 3.3 m/s2
C
An 800-N box is pushed up an inclined plane. The plane is 4.0 m long and rises 2.0 m. It requires 3200 J of work to get the box to the top of the plane. What was the magnitude of the average friction force on the box? A) 0 N B) non-zero, but less than 400 N C) 400 N D) greater than 400 N
C
An object is moving with constant non-zero acceleration in the +x axis. The velocity versus time graph of this object is A) a horizontal straight line. B) a vertical straight line. C) a straight line making an angle with the time axis. D) a parabolic curve.
C
An object of mass 6000 kg rests on the flatbed of a truck. It is held in place by metal brackets that can exert a maximum horizontal force of 9000 N. When the truck is traveling 15 m/s, what is the minimum stopping distance if the load is not to slide forward into the cab? A) 15 m B) 30 m C) 75 m D) 150 m
C
Consider two masses m1 and m2 at the top of two frictionless inclined planes. Both masses start from rest at the same height. However, the plane on which m1 sits is at an angle of 30e with the horizontal, while the plane on which m2 sits is at 60e. If the masses are released, which is going faster at the bottom of its plane? A) m1 B) m2 C) They both are going the same speed. D) cannot be determined without knowing the masses
C
If you blow up a balloon, and then release it, the balloon will fly away. This is an illustration of A) Newton's first law. B) Newton's second law. C) Newton's third law. D) Galileo's law of inertia.
C
In the Atwood machine shown in Fig. 4-1, if M = 0.60 kg and m = 0.40 kg, what is the magnitude of the acceleration of the system? (Ignore friction and the mass of the pulley.) A) 5.3 m/s2 B) 3.9 m/s2 C) 2.0 m/s2 D) 0.98 m/s2
C
Matthew pulls his little sister Sarah in a sled on an icy surface (assume no friction), with a force of 60.0 N at an angle of 37.0e upward from the horizontal. If he pulls her a distance of 12.0 m, what is the work done by Matthew? A) 185 J B) 433 J C) 575 J D) 720 J
C
On a plot of Force versus position (F vs. x), what represents the work done by the force F? A) the slope of the curve B) the length of the curve C) the area under the curve D) the product of the maximum force times the maximum x
C
Starting from rest, a 4.0-kg body reaches a speed of 8.0 m/s in 2.0 s. What is the net force acting on the body? A) 4.0 N B) 8.0 N C) 16 N D) 32 N
C
The acceleration of gravity on the Moon is only one-sixth of that on Earth. If you hit a baseball on the Moon with the same effort (and at the speed and angle) that you would on Earth, the ball would land A) the same distance away. B) one-sixth as far. C) 6 times as far. D) 36 times as far.
C
The area under a curve in a velocity versus time graph gives A) acceleration. B) velocity. C) displacement. D) position.
C
The coefficients of static and kinetic frictions for plastic on wood are 0.50 and 0.40, respectively. How much horizontal force would you need to apply to a 3.0 N plastic calculator to start it moving from rest? A) 0.15 N B) 1.2 N C) 1.5 N D) 2.7 N
C
Two cars collide head-on. At every moment during the collision, the magnitude of the force the first car exerts on the second is exactly equal to the magnitude of the force the second car exerts on the first. This is an example of A) Newton's first law. B) Newton's second law. C) Newton's third law. D) Newton's law of gravitation.
C
Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street? A) The one thrown up is traveling faster. B) The one thrown down is traveling faster. C) They are traveling at the same speed. D) It is impossible to tell because the height of the building is not given
C
What is the correct unit of power expressed in SI units? A) kg m/s2 B) kg m2/s2 C) kg m2/s3 D) kg2 m/s2
C
What is the correct unit of work expressed in SI units? A) kg m/s2 B) kg m2/s C) kg m2/s2 D) kg2 m/s2
C
You throw a ball straight up. Compare the sign of the work done by gravity while the ball goes up with the sign of the work done by gravity while it goes down. A) Work is + on the way up and + on the way down. B) Work is + on the way up and - on the way down. C) Work is - on the way up and + on the way down. D) Work is - on the way up and - on the way down.
C
A 12-kg object is moving on a rough, level surface. It has 24 J of kinetic energy. The friction force on it is a constant 0.50 N. How far will it slide? A) 2.0 m B) 12 m C) 24 m D) 48 m
D
A 50-N object was lifted 2.0 m vertically and is being held there. How much work is being done in holding the box in this position? A) more than 100 J B) 100 J C) less than 100 J, but more than 0 J D) 0 J
D
A block of mass M slides down a frictionless plane inclined at an angle q with the horizontal. The gravitational force is directed A) parallel to the plane in the same direction as the movement of the block. B) parallel to the plane in the opposite direction as the movement of the block C) perpendicular to the plane. D) toward the center of the Earth.
D
A boat can move at 30 km/h in still water. How long will it take to move 12 km upstream in a river flowing 6.0 km/h? A) 20 min B) 22 min C) 24 min D) 30
D
A boat, whose speed in still water is 8.0 m/s, is directed across a river with a current of 6.0 m/s. What is the speed of the boat as it crosses the river? A) 5.3 m/s B) 6.0 m/s C) 8.0 m/s D) 10.0 m/s
D
A force of 10 N is applied horizontally to a 2.0-kg mass on a level surface. The coefficient of kinetic friction between the mass and the surface is 0.20. If the mass is moved a distance of 10 m, what is the change in its kinetic energy? A) 20 J B) 39 J C) 46 J D) 61 J
D
A person on a scale rides in an elevator. If the mass of the person is 60.0 kg and the elevator accelerates upward with an acceleration of 4.90 m/s2, what is the reading on the scale? A) 147 N B) 294 N C) 588 N D) 882 N
D
A rocket moves through empty space in a straight line with constant speed. It is far from the gravitational effect of any star or planet. Under these conditions, the force that must be applied to the rocket in order to sustain its motion is A) equal to its weight. B) equal to its mass. C) dependent on how fast it is moving. D) zero.
D
A stone is thrown straight up. At the top of its path, the net force acting on it is A) greater than its weight. B) greater than zero, but less than its weight. C) instantaneously equal to zero. D) equal to its weight.
D
An Olympic athlete throws a javelin at four different angles above the horizontal, each with the same speed: 30e, 40e, 60e, and 80e. Which two throws cause the javelin to land the same distance away? A) 30e and 80e B) 40e and 60e C) 40e and 80e D) 30e and 60e
D
An object is released from rest a height h above the ground. A second object with four times the mass of the first if released from the same height. The potential energy of the second object compared to the first is A) one-fourth as much. B) one-half as much. C) twice as much. D) four times as much.
D
Can work be done on a system if there is no motion? A) Yes, if an outside force is provided. B) Yes, since motion is only relative. C) No, since a system which is not moving has no energy. D) No, because of the way work is defined.
D
Does the centripetal force acting on an object do work on the object? A) Yes, since a force acts and the object moves, and work is force times distance. B) Yes, since it takes energy to turn an object. C) No, because the object has constant speed. D) No, because the force and the displacement of the object are perpendicular.
D
If the position versus time graph of an object is a vertical line, the object is A) moving with constant non-zero speed. B) moving with constant non-zero acceleration. C) at rest. D) moving with infinite speed.
D
If you exert a force F on an object, the force which the object exerts on you will A) depend on whether or not the object is moving. B) depend on whether or not you are moving. C) depend on the relative masses of you and the object. D) always be F.
D
If you push twice as hard against a stationary brick wall, the amount of work you do A) doubles. B) is cut in half. C) remains constant but non-zero. D) remains constant at zero.
D
If you walk 5.0 m horizontally forward at a constant velocity carrying a 10-N object, the amount of work you do is A) more than 50 J. B) equal to 50 J. C) less than 50 J, but more than 0 J. D) zero.
D
In the absence of an external force, a moving object will A) stop immediately. B) slow down and eventually come to a stop. C) go faster and faster. D) move with constant velocity.
D
It's more difficult to start moving a heavy carton from rest than it is to keep pushing it with constant velocity, because A) the normal force is greater when the carton is at rest. B) ms < mk. C) initially, the normal force is not perpendicular to the applied force. D) mk < ms.
D
The quantity Fd/t is A) the kinetic energy of the object. B) the potential energy of the object. C) the work done on the object by the force. D) the power supplied to the object by the force.
D
When the rocket engines on the starship NO-PAIN-NO-GAIN are suddenly turned off, while traveling in empty space, the starship will A) stop immediately. B) slowly slow down, and then stop. C) go faster and faster. D) move with constant speed.
D
State Newton's three laws.
Newton's first law: Every object continues in its state of rest, or of uniform velocity straight line, as long as no net force acts on it. Newton's second law: The acceleration of an object is directly proportional to the net force acting on it, and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object. Newton's third law: Whenever one object exerts a force on a second object, the second exerts an equal force in the opposite direction on the first.