Physics Exam 2
95) As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?
A) 1
The Aswan High Dam on the Nile River in Egypt is 111 m high. What is the gauge pressure in the water at the foot of the dam? The density of water is 1000 kg/m3.
A) 1.09 × 10^6 Pa
The Tonga Trench in the Pacific Ocean is 36,000 feet deep. Assuming that sea water has an average density of 1.04 g/cm3, calculate the absolute (total) pressure at the bottom of the trench in atmospheres. (1.00 in = 2.54 cm, 1.00 atm = 1.01 × 10^5 Pa)
A) 1.1 × 103 atm
In a police ballistics test, a 10.0-g bullet moving at 300 m/s is fired into a 1.00-kg block at rest. The bullet goes through the block almost instantaneously and emerges with 50.0% of its original speed. What is the speed of the block just after the bullet emerges?
A) 1.50 m/s
completely upside down. If the radius of the loop is with what minimum speed must the car traverse the loop so that the rider does not fall out while upside down at the top? Assume the rider is not strapped to the car.
A) 11.4m/s
A 328 kg car moving at 19.1 m/s in the x-direction hits from behind a second car moving at 13.0 m/s in the same direction. If the second car has a mass of 790 kg and a speed of 15.1 m/s right after the collision, what is the velocity of the first car after this sudden collision?
A) 14.0 m/s
123) The figure shows a person's foot. In that figure, the Achilles tendon exerts a force of magnitude F = 720 N. What is the magnitude of the torque that this force produces about the ankle joint?
B) 16 N*m
An object floats with half its volume beneath the surface of the water. The weight of the displaced water is 2000 N. What is the weight of the object? The density of water is 1000 kg/m3.
B) 2000 N
133) A store's sign has a mass of 20 kg and is 3.0 m long. It is uniform, so its center of gravity is at the center of the sign. It is supported horizontally by a small loose bolt attached to the wall at one end and by a wire at the other end, as shown in the figure. What is the tension in the wire?
B) 230 N
A child is riding a merry-go-round that is turning at 7.18 rpm. If the child is standing 4.65 m from the center of the merry-go-round, how fast is the child moving?
B) 3.50 m/s
An old 78 rpm record rotates through an angle of 320° as it slows down uniformly from 78.0 rpm to 22.8 rpm. What is the magnitude of the angular acceleration of the record?
B) 5.46 rad/s^2
A scooter has wheels with a diameter of 120 mm. What is the angular speed of the wheels when the scooter is moving forward at 6.00 m/s?
B) 955 rpm
89) The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis perpendicular to the plane of the drawing at point P?
B) B
The weight of a 1200-kg car is supported equally by the four tires, which are inflated to the same gauge pressure. What gauge pressure is required so the area of contact of each tire with the road is 100 cm^2?
C) 2.9 × 10^5 Pa
A 0.10-kg ball, traveling horizontally at 25 m/s, strikes a wall and rebounds at 19 m/s. What is the magnitude of the change in the momentum of the ball during the rebound?
C) 4.4 kg*m/s
Consider a uniform hoop of radius R and mass M rolling without slipping. Which is larger, its translational kinetic energy or its rotational kinetic energy?
C) Both are equal.
The water pressure to an apartment is increased by the water company. The water enters the apartment through an entrance valve at the front of the apartment. Where will the increase in the static water pressure be greatest when no water is flowing in the system?
C) It will be the same at all faucets.
Two wires are made out of the same metal, but one wire is twice as long as the other wire. Which wire will have the greatest elastic modulus?
C) It will be the same for both wires.
Two cars go around a banked curve at the proper speed for the banking angle. One car has tires with excellent traction, while the other car has bald slippery tires. Which of these cars is more likely to slide on the pavement as it goes around the curve?
C) Neither car will slide
If atmospheric pressure increases by an amount Δp, which of the following statements about the pressure in a lake is true? (There could be more than one correct choice.)
C) The absolute (total) pressure increases by Δp. E) The gauge pressure does not change.
As a rock sinks deeper and deeper into water of constant density, what happens to the buoyant force on it if it started above the surface of the water?
C) The buoyant force first increases and then remains constant.
Salt water has greater density than fresh water. A boat floats in both fresh water and in salt water. Where is the buoyant force greater on the boat?
C) The buoyant force is the same in both cases.
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?
C) The lead ball will float with about 17% of its volume above the surface of the mercury.
A small car meshes with a large truck in a head-on collision. Which of the following statements concerning the magnitude of the momentum change during the collision is correct? (There could be more than one correct choice.)
C) The small car and the truck experience the same magnitude momentum change.
In a collision between two unequal masses, which mass receives a greater magnitude impulse?
C) They receive equal impulses.
45) In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is
C) completely inelastic.
Identical forces act for the same length of time on two different objects. The magnitude of the change in momentum of the lighter object is
C) exactly equal to the magnitude of the change in momentum of the larger mass.
96) Five forces act on a rod that is free to pivot at point P, as shown in the figure. Which of these forces is producing a counter-clockwise torque about point P? (There could be more than one correct choice.)
C) force C
The momentum of an isolated system is conserved
C) in both elastic and inelastic collisions
When an object moves in uniform circular motion, the direction of its acceleration is
C) is directed toward the center of its circular path
Which of the following quantities are units of impulse? (There could be more than one correct choice.)
C) kg*m/s D) N*s
Which of the following quantities are units of momentum? (There could be more than one correct choice.)
C) kg*m/s D) N*s
You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it
C) moves along a straight-line path in its original direction.
On a horizontal frictionless air table, a puck runs into an ideal horizontal spring that is fastened to the table. The puck compresses the spring by 15 cm before coming to rest. During the compression process, which quantities are conserved?
C) only the mechanical energy (kinetic plus potential) of the puck
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
C) remain where it is released.
52) Three objects are moving along a straight line as shown in the figure. Taking the positive direction to be to the right, what is the total momentum of this system?
D) -14.0 kg*m/s
What buoyant force does a 0.60-kg solid gold crown experience when it is immersed in water? The density of gold is 19.3 × 103 kg/m3 and that of water is 1000 kg/m3.
D) 0.30 N
A 100-g ball falls from a window that is 12 m above ground level and experiences no significant air resistance as it falls. What is its momentum when it strikes the ground?
D) 1.5 kg*m/s
A 4.0-kg cylinder of solid iron is supported by a string while submerged in water. What is the tension in the string? The density of iron is 7860 kg/m3 and that of water is 1000 kg/m3.
D) 34 N
A polar bear of mass 200 kg stands on an ice floe that is a uniform 1.0 m thick. What is the minimum area of the floe that will just support the bear in saltwater of density 1030 kg/m3? The density of ice is 980 kg/m3.
D) 4.0 m2
117) In the figure, point P is on the rim of a wheel of radius 2.0 m. At time t = 0, the wheel is at rest, and P is on the x-axis. The wheel undergoes a uniform counterclockwise angular acceleration of 0.010 rad/s2 about the center O. (a) At time t = 0, what is the tangential acceleration of P? (b) What is the linear speed of P when it reaches the y-axis? (c) What is the magnitude of the net linear acceleration of P when it reaches the y-axis? (d) How long after starting does it take for P to return to its original position on the x-axis?
(a) 0.020 m/s2 (b) 0.35 m/s (c) 0.066 m/s2 (d) 35 s
67) Jennifer hits a stationary 0.20-kg ball, and it leaves her racket at 40 m/s. Time-lapse photography shows that the ball was in contact with the racket for 40 ms. (a) What average force did the ball exert on the racket? (b) What is the ratio of this force to the weight of the ball?
(a) 0.20kN (b) 100
When Mary is 3.00 m from the center of a merry-go-round, her tangential speed is a constant 1.88 m/s. (a) What is her angular speed in rad/s? (b) What is the magnitude of her linear acceleration?
(a) 0.627 rad/s (b) 1.18 m/s2
When an old LP turntable was revolving at 33 1/3 rpm, it was shut off and uniformly slowed down and stopped in 5.5 seconds. (a) What was the magnitude of its angular acceleration (in rad/s2) as it slowed down? (b) Through how many revolutions did it turn while stopping?
(a) 0.63 rad/s2 (b) 1.5 rev
A wheel of diameter 0.70 m rolls on the floor without slipping. A point at the top of the wheel moves with a speed 2.0 m/s relative to the floor. (a) At what speed is the central axis of the wheel moving relative to the floor? (b) What is the angular speed of the wheel?
(a) 1.0 m/s (b) 2.9 rad/s
In a perfectly elastic collision, a 400-g ball moving toward the east at 3.7 m/s suddenly collides head-on with a 200 g ball sitting at rest. (a) Determine the velocity of the first ball just after the collision. (b) Determine the velocity of the second ball just after the collision. (c) Is kinetic energy conserved in this collision? How do you know?
(a) 1.2 m/s toward the east (b) 4.9 m/s toward the east (c) Yes, it is an elastic collision.
In a police rifle test, a 15-g bullet traveling 213 m/s in a vertical direction suddenly buries itself in a 2.4-kg block of wood at rest directly above it. As a result, the bullet-block combination moves vertically upward. (a) Determine the velocity of the bullet-block combination just after the impact. (b) Determine the maximum height reached by the bullet/block combination. (c) Is kinetic energy conserved in this collision?
(a) 1.3 m/s (b) 0.089 m (c) No, this is an inelastic collision.
113) A wheel accelerates with a constant angular acceleration of 4.5 rad/s2 from an initial angular speed of 1.0 rad/s. (a) Through what angle does the wheel turn in the first 2.0 s, and (b) what is its angular speed at that time?
(a) 11 rad (b) 10 rad/s
138) A cubical block of stone is lowered at a steady rate into the ocean by a crane, always keeping the top and bottom faces horizontal. Which one of the following graphs best describes the gauge pressure p on the bottom of this block as a function of time t if the block just enters the water at time t = 0 s?
A
A bowling ball of mass 7.5 kg and diameter 18 cm rolls without slipping down a 10-m bowling lane with a constant speed 4.3 m/s. (a) Through what angle does the bowling ball turn as it travels the length of the lane? (b) What is the angular speed of the bowling ball? (c) Calculate the maximum radial acceleration that a point on the surface of the bowling ball could have. Calculate the tangential acceleration of a point on the surface of the bowling ball.
(a) 110 rad (b) 48 rad/s (c) 210 m/s2 (d) 0 m/s2
A car is traveling along a freeway at 65 mph. What is the linear speed, relative to the highway, of each of the following points on one of its tires? (a) the highest point on the tire (b) the lowest point on a tire (c) the center of the tire
(a) 130 mph (b) 0 mps (c) 65 mph
A centrifuge in a medical laboratory rotates at a rotational speed of 3600 rev/min. When switched off, it makes 50 complete turns at a constant angular acceleration before coming to rest. (a) What was the magnitude of the angular acceleration of the centrifuge as it slowed down? (d) How long did it take for the centrifuge to come to rest after being turned off?
(a) 230 rad/s2 (b) 1.7 s
A curved portion of highway has a radius of curvature of 65 m. As a highway engineer, you want to bank this curve at the proper angle for a steady speed of 22 m/s. (a) What banking angle should you specify for this curve? (b) At the proper banking angle, what normal force and what friction force does the highway exert on a 750-kg car going around the curve at the proper speed?
(a) 37° (b) 9200N (normal force), 0 N (friction)
A small 175-g ball on the end of a light string is revolving uniformly on a frictionless surface in a horizontal circle of diameter 1.0 m. The ball makes 2.0 revolutions every 1.0 s. (a) What are the magnitude and direction of the acceleration of the ball? (b) Find the tension in the string.
(a) 79.0 m/s^2 toward the center of the circle (b) 13.8N
An artificial satellite in a low orbit circles the earth every 98 minutes. What is its angular speed in rad/s?
0.0011 rad/s
In a police ballistics test, 2.00-g bullet traveling at 700 m/s suddenly hits and becomes embedded in a stationary 5.00-kg wood block. What is the speed of the block immediately after the bullet has stopped moving relative to the block?
0.280 m/sA
A majorette fastens two batons together at their centers to form an X shape. Each baton consists of an extremely light 1.2-m bar with small 0.25-kg balls at each end. What is the moment of inertia of this baton about an axis through the center of the X?
0.36 kg ∙ m^2
A 60-kg swimmer suddenly dives horizontally from a 150-kg raft with a speed of 1.5 m/s. The raft is initially at rest. What is the speed of the raft immediately after the diver jumps if the water has negligible effect on the raft?
0.60 m/s
A bicycle wheel has an initial angular speed of 7.2 rad/s. After turning through of a revolution, the angular speed is reduced to 2.2 rad/s. If the angular acceleration of the wheel was constant during the motion, how long will it take the wheel to make the one-half revolution?
0.67 s
A wheel starts from rest and has a uniform angular acceleration of 4.0 rad/s2. After the wheel completes its first revolution, how long does it take for it to make its second complete revolution?
0.73 s
A 14,000-kg boxcar is coasting at 1.50 m/s along a horizontal track when it suddenly hits and couples with a stationary 10,000-kg boxcar. What is the speed of the cars just after the collision?
0.875 m/s
A small ball is tied to one end of a light 2.5-m wire, and the other end of the wire is hooked to the ceiling. A person pulls the ball to the side until the wire makes an angle of 35° with the plane of the ceiling and then gently releases it. What is the angular speed of the ball, in rad/s, as it swings through its lowest point?
1.8 rad/s
A very dense 1500-kg point mass (A) and a dense 1200-kg point mass (B) are held in place 1.00 m apart on a frictionless table. A third point mass is placed between the other two at a point that is 20.0 cm from B along the line connecting A and B. When the third mass is suddenly released, find the magnitude and direction (toward A or toward B) of its initial acceleration. (G = 6.67 × 10-11 N ∙ m2/kg2)
1.8 x 10^-6 m/s^2, towards B
172) A container consists of two vertical cylindrical columns of different diameter connected by a narrow horizontal section, as shown in the figure. The open faces of the two columns are closed by very light plates that can move up and down without friction. The tube diameter at A is 35.0 cm and at B it is 10.2 cm. This container is filled with oil of density 0.820 g/cm3. If a 125kg object is placed on the larger plate at A, how much mass should be placed on the smaller plate at B to balance it?
10.6 kg
A car (of mass 1500 kg) and a small truck (of mass 2000 kg) collide suddenly at right angles at an icy intersection. The car was originally traveling eastward at 20.0 m/s and the truck was traveling northward at 20.0 m/s just before the collision took place. What is the speed of the combined wreck just after the collision if the vehicles become enmeshed?
14.3 m/s
A 0.17-kg baseball is thrown with a speed of 38 m/s and it is hit straight back toward the pitcher with a speed of 62 m/s. What is the magnitude of the impulse exerted upon the ball by the bat?
17 N*s
122) The figure shows two blocks connected by a light cord over a pulley. This apparatus is known as an Atwood's machine. There is no slipping between the cord and the surface of the pulley. The pulley itself has negligible friction and it has a radius of 0.12 m and a mass of 10.3 kg. We can model this pulley as a solid uniform disk. At the instant that the heavier block has descended 1.5 m starting from rest, what is the speed of the lighter block?
2.4 m/s
What is the magnitude of the gravitational force that two small 7.00-kg balls exert on each other when they are 35.0 cm apart? (G = 6.67 × 10-11 N ∙ m2/kg2)
2.67 x 10^-8
The diameter of the Moon is 3.47 × 106 m, and it subtends an angle of 0.00904 rad when viewed from the surface of Earth. How far is the Moon from Earth?
3.84 × 10^8 m
A bicycle wheel has an outside diameter of 66 cm. Through what distance does a point on the rim move as the wheel rotates through an angle of 70°?
40 cm
A Ferris wheel has radius 5.0 m and makes one revolution every 8.0 s with uniform rotation. A person who normally weighs 670 N is sitting on one of the benches attached at the rim of the wheel. What is the apparent weight (the normal force exerted on her by the bench) of the person as she passes through the highest point of her motion?
460N
A batter hits a 0.140-kg baseball that was approaching him at 30 m/s and, as a result, the ball leaves the bat at 40 m/s in the reverse of its original direction. The ball remains in contact with the bat for 2.0 ms. What is the magnitude of the average force exerted by the bat on the ball?
4900 N
A force of 5.3 N is needed to hold on to an umbrella in a strong wind. If the air molecules each have a mass of 4.7 ×10-26 kg, and each one strikes the umbrella (without rebounding) with a speed of 2.0 m/s in the same direction, how many atoms strike the umbrella each second? Assume that the wind blows horizontally so that the gravity can be neglected
5.6x10^25 per second
An 80-kg man is skating northward and happens to suddenly collide with a 20-kg boy who is ice skating toward the east. Immediately after the collision, the man and boy are seen to be moving together at 2.5 m/s in a direction 60° north of east. How fast was the boy moving just before the collision?
6.3 m/s
Two identical tiny balls of highly compressed matter are 1.50 m apart. When released in an orbiting space station, they accelerate toward each other at 2.00 cm/s2. What is the mass of each of them? (G = 6.67 × 10-11 N ∙ m2/kg2)
6.75 x 10^8 kg
85) Three balls are moving along a straight line having the instantaneous positions shown in the figure. At that instant, find the location and velocity of the center of mass (or center of gravity) of this system.
7.00 m to the right of the 2.00 kg ball, 1.11 m/s to the right
A 2200-kg auto moving northward at 12.0 m/s runs into a 3800-kg truck which is also moving northward, but at 5.00 m/s. If the vehicles lock bumpers, how fast are they moving just after the collision?
7.57 m/s
A 475-gram ball is traveling horizontally at 12.0 m/s to the left when it is suddenly struck horizontally by a bat, causing it to reverse direction and initially travel at 8.50 m/s to the right. If the bat produced an average force of 1275 N on the ball, for how long (in milliseconds) was it in contact with the ball?
7.64 ms
An empty train car of mass 2.0 x 104 kg coasts along at 10 m/s. A 3000-kg boulder is suddenly dropped vertically into the car. Find the speed of the car immediately after the boulder is dropped in.
8.7 m/s
Two astronauts, of masses 60 kg and 80 kg, are initially right next to each other and at rest in outer space. They suddenly push each other apart. How far has the heavier astronaut moved when the lighter astronaut has moved 12 m?
9.0 m
Pulling out of a dive, the pilot of an airplane guides his plane into a vertical circle. At the bottom of the dive, the speed of the airplane is 320 m/s. What is the smallest radius allowable for the vertical circle if the pilot's apparent weight is not to exceed 7.0 times his true weight?
A) 1700m
A 600-kg car makes a 90° turn. Its speed before the turn is 21.0 m/s and after the turn it is 24.0 m/s. What is the magnitude of the change in the car's momentum during the turn?
A) 19.1 x10^3 kg*m/s
Calculate the pressure exerted on the ground due to the weight of 79 kg person standing on one foot. if the bottom of the person's foot is 13 cm wide and 28 cm long.
A) 2.1 × 10^4 Pa
74) A block of mass m = 5.6 kg, moving on a frictionless surface with a velocity of vi=6.5 m/s to the right, collides with a block of mass M at rest, as shown in the figure. After the collision, the 5.6-kg block recoils with a velocity of vf= 0.70 m/s to the left. If the blocks are in contact for 0.20 s, what is the magnitude of the average force on the 5.6-kg block, while the two blocks are in contact?
A) 202N
169) A container has a vertical tube, whose inner radius is 24.00 mm, connected to it at its side, as shown in the figure. An unknown liquid reaches level A in the container and level B in the tube-level A being 5.0 cm higher than level B. The liquid supports a 20-cm high column of oil, between levels B and C, whose density is 570 kg/m^3. The mass of the oil is closest to
A) 210
One way that future space stations may create artificial gravity is by rotating the station. Consider a cylindrical space station 380 m in diameter that is rotating about its longitudinal axis. Astronauts walk on the inside surface of the space station. How long will it take for each rotation of the cylinder if it is to provide "normal" gravity for the astronauts?
A) 28s
A water tank is filled to a depth of 10 m, and the bottom of the tank is 20 m above ground. A water-filled hose that is 2.0 cm in diameter extends from the bottom of the tank to the ground, but no water is flowing in this hose. The water pressure at ground level in the hose is closest to which of the following values? The density of water is 1000 kg/m3.
A) 3.9 × 105 N/m2
72) A block of mass m = 34 kg and speed V is behind a block of mass M = 81 kg and speed of 0.50 m/s as shown in the figure. The surface is frictionless and the blocks collide and couple. After the collision, the blocks have a common speed of 0.90 m/s. What is the magnitude of the impulse on the 34-kg block due to the collision?
A) 32 N*s
The curved section of a speedway is a circular arc having a radius of 190 m. This curve is properly banked for racecars moving at 34 m/s. At what angle with the horizontal is the curved part of the speedway banked?
A) 32°
Pulling out of a dive, the pilot of an airplane guides his plane into a vertical circle with a radius of 600 m. At the bottom of the dive, the speed of the airplane is 150 m/s. What is the apparent weight of the 70-kg pilot at that point?
A) 3300N
171) A container has a vertical tube, whose inner radius is 20.00 mm, connected to it at its side, as shown in the figure. An unknown liquid reaches level A in the container and level B in the tube-level A being 5.0 cm higher than level B. The liquid supports a 20-cm high column of oil, between levels B and C, whose density is The density of the unknown liquid is closest to
A) 3600 kg/m^3
A chicken is running in a circular path with an angular speed of 1.52 rad/s. How long does it take the chicken to complete one revolution?
A) 4.13 s
One of the dangers of tornados and hurricanes is the rapid drop in air pressure that is associated with such storms. Assume that the air pressure inside of a sealed house is 1.02 atm when a hurricane hits. The hurricane rapidly decreases the external air pressure to 0.910 atm. What net outward force is exerted on a square window of the house that is 2.03 m on each side? (1.00 atm = 1.01 × 105 Pa)
A) 4.59 × 10^4 N
A round coin has a diameter of 19.55 mm, a thickness of 1.55 mm, and a mass of 2.50 g. What is its density?
A) 5.37 × 10^3 kg/m^3
The density of material at the center of a neutron star is approximately 1.00 × 1018 kg/m3. What is the mass of a cube of this material that is 1.76 microns on each side. (One micron is equal to 1.00 × 10-6 m.)
A) 5.45 kg
What force does the water exert (in addition to that due to atmospheric pressure) on a submarine window of radius 44.0 cm at a depth of 9400 m in sea water? The density of sea water is 1025 kg/m3.
A) 5.74 × 107 N
What is the gravitational force acting on a 59-kg person due to another 59-kg person standing 2.0 m away? We can model each person as a small sphere. (G = 6.67 × 10-11 N ∙ m2/kg2)
A) 5.8x10^-8 N
A machinist turns on the power on to a grinding wheel at time t = 0 s. The wheel accelerates uniformly from rest for 10 s and reaches the operating angular speed of The wheel is run at that angular velocity for 30 s, and then power is shut off. The wheel slows down uniformly at 1.4 rad/s^2 until the wheel stops. What is the total number of revolutions made by the wheel in this situation?
A) 510
The curved section of a horizontal highway is a circular unbanked arc of radius 740 m. If the coefficient of static friction between this roadway and typical tires is 0.40, what would be the maximum safe driving speed for this horizontal curved section of highway?
A) 54m/s
79) A block of mass m = 3.6 kg, moving on a frictionless surface with a speed vi=9.3 m/s makes a sudden perfectly elastic collision with a stationary block of mass M, as shown in the figure. Just after the collision, the 3.6-kg block recoils with a speed of vf=2.7 m/s. What is the speed V of the other block?
A) 6.6 m/s
A container has a vertical tube, whose inner radius is 12.00 mm, connected to it at its side, as shown in the figure. An unknown liquid reaches level A in the container and level B in the tube-level A being 5.0 cm higher than level B. The liquid supports a 20-cm high column of oil, between levels B and C, whose density is 320 kg/m^3. The gauge pressure at level B is closest to
A) 630 Pa
Through how many degrees does a 33 rpm turntable rotate in 0.32s ?
A) 63°
78) A block of mass m = 4.4 kg, moving on frictionless surface with a speed makes a sudden perfectly elastic collision with a second block of mass M, as shown in the figure. The second block is originally at rest. Just after the collision, the 4.4-kg block recoils with a speed of What is the mass M of the second block?
A) 7.7 kg
A girl of mass 55 kg throws a ball of mass 0.80kg against a wall. The ball strikes the wall horizontally with a speed of 25 m/s, and it bounces back with this same speed. The ball is in contact with the wall 0.050s. What is the magnitude of the average force exerted on the wall by the ball?
A) 800 N
What is the angular speed, in rad/s, of a flywheel turning at 813.0 rpm?
A) 85.14 rad/s
A 1000-kg car is moving at 30 m/s around a horizontal unbanked curve whose diameter is 0.20 km. What is the magnitude of the friction force required to keep the car from sliding?
A) 9000N
A closed cubical chamber resting on the floor contains oil and a piston. If you push down on the piston hard enough to increase the pressure just below the piston by an amount Δp, which of the following statements is correct? (There could be more than one correct choice.)
A) The pressure everywhere in the oil will increase by Δp. E) The increase in the force on the top of the chamber will be the same as the increase in the force on the bottom of the chamber.
Which one of the following is an accurate statement?
A) The ratio of tensile stress to tensile strain is called Young's modulus.
When a rigid object rotates about a fixed axis, what is true about all the points in the object? (There could be more than one correct choice.)
A) They all have the same angular speed. C) They all have the same angular acceleration
Consider a solid uniform sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational?
A) Translational kinetic energy is larger.
In an inelastic collision involving an isolated system, the final total momentum is
A) exactly the same as the initial momentum.
A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by pulling in her arms. Which of the following statements are true about the skater during this process? (There could be more than one correct choice.)
A) her angular momentum remains constant
An air bubble underwater has the same pressure as that of the surrounding water. As the air bubble rises toward the surface (and its temperature remains constant), the volume of the air bubble
A) increases.
43) In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is
A) perfectly elastic
A 10-kg piece of aluminum sits at the bottom of a lake, right next to a 10-kg piece of lead, which is much denser than aluminum. Which one has the greater buoyant force on it?
A) the aluminum
A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which one of these objects experiences the greater momentum change?
A) the ball
Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude?
A) the first force (at the midpoint)
A rubber ball bounces off of a wall with an initial speed v and reverses its direction so its speed is v right after the bounce. As a result of this bounce, which of the following quantities of the ball are conserved? (There could be more than one correct choice.)
A) the kinetic energy of the ball
A waiter fills your water glass with ice water (containing many ice cubes) such that the liquid water is perfectly level with the rim of the glass. As the ice melts,
A) the liquid-water level remains flush with the rim of the glass.
A 5-kg ball collides inelastically head-on with a 10-kg ball, which is initially stationary. Which of the following statements is true? (There could be more than one correct choice.)
A) the magnitude of the change of velocity the 5-kg ball experience is greater than that of the 10-kg ball. D) The magnitude of the change of the momentum of the 5-kg ball is equal to the magnitude of the 10-kg ball.
When a car goes around a banked circular curve at the proper speed for the banking angle, what force cause it to follow the circular path?
A) the normal force from the road
Tensile strain is
A) the ratio of the change in length to the original length.
If you stood on a planet having a mass four times that of Earth's mass, and a radius two times that of Earth's radius, you weigh
A) the same as you do on Earth
A 0.330-kg volleyball is thrown vertically downward with a speed of 0.150 m/s in a place where g = 9.81 m/s2. It takes it 0.0655 s to reach the ground. What is the magnitude of its momentum just before it hits the ground?
B) 0.262 kg*m/s
Two ice skaters suddenly push off against one another starting from a stationary position. The 45-kg skater acquires a speed of 0.375 m/s relative to the ice. What speed does the 60-kg skater acquire relative to the ice?
B) 0.28 m/s
A 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance?
B) 0.88 kg*m/s
A rolling wheel of diameter of 68 cm slows down uniformly from 8.4 m/s to rest over a distance of 115 m. What is the magnitude of its angular acceleration if there was no slipping?
B) 0.90 rad/s2
You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You have two choices about what to do with the ball: either catch the ball or deflect it back toward your friend with the same speed as it was originally thrown. Which choice should you make in order to maximize your speed on the skateboard?
B) Deflect the ball back
If you swing a bucket of water fast enough in vertical circle, at the highest point the water does not spill out. This happens because an outward force balances the pull of gravity on the water.
B) False
Two children, Ahmed and Jacques, ride on a merry-go-round. Ahmed is at a greater distance from the axis of rotation than Jacques. Which of the following are true statements? (There could be more than one correct choice.)
B) Jacques and Ahmed have the same angular speed. D) Ahmed has a greater tangential speed than Jacques.
A disk and a hoop of the same mass and radius are released at the same time at the top of an inclined plane. If both are uniform, which one reaches the bottom of the incline first if there is no slipping?
B) The disk
125) A croquet mallet balances when suspended from its center of mass, as shown in the left part of the figure. If you cut the mallet into two pieces at its center of mass, as shown in the right part of the figure, how do the masses of the two pieces compare? (There could be more than one correct choice.)
B) The piece with the head of the mallet has the greater mass. D) It is impossible to tell.
A rocket explodes into two fragments, one 25 times heavier than the other. The magnitude of the momentum change of the lighter fragment is
B) The same as the momentum change of the heavier fragment.
129) The graph in the figure shows the tensile stress as a function of the tensile strain in a certain wire. What does the slope of this graph give us for this wire?
B) Young's modulus for the material of the wire
In a game of pool, the white cue ball hits the #5 ball and stops, while the #5 ball moves away with the same velocity as the cue ball had originally. Both balls have the same mass. This type of collision is
B) elastic
A boat loaded with rocks is floating in a swimming pool. If the rocks are thrown into the pool, the water level in the pool, after the rocks have settled to the bottom,
B) falls.
A railroad car collides with and sticks to an identical railroad car that is initially at rest. After the collision, the kinetic energy of the system
B) is half as much as before.
93) A uniform ball is released from rest on a no-slip surface, as shown in the figure. After reaching its lowest point, the ball begins to rise again, this time on a frictionless surface. When the ball reaches its maximum height on the frictionless surface, it is
B) lower than when it was released.
Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake. The person in the front throws a very massive ball toward the back, and the person in the back catches it. After the ball is caught, the canoe is
B) stationary
The reason an astronaut in an earth satellite feels weightless is that
B) the astronaut is falling
97) The rotating systems shown in the figure differ only in that the two identical movable masses are positioned a distance r from the axis of rotation (left), or a distance r/2 from the axis of rotation (right). If you release the hanging blocks simultaneously from rest,
B) the block at the right lands first.
When a car goes around a circular curve on a horizontal road at constant speed, what force causes it to follow the circular path?
B) the friction from the road
Suppose a solid uniform sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The angular velocity of the sphere at the bottom of the incline depends on
B) the radius of the sphere.
139) A cubical block of stone is lowered at a steady rate into the ocean by a crane, always keeping the top and bottom faces horizontal. Which one of the following graphs best describes the absolute (total) pressure p on the bottom of this block as a function of time t if the block just enters the water at time t = 0 s?
C
A 0.140-kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground and bounces. It rebounds with an upward velocity of 1.00 m/s. What is the change of the ball's momentum during the bounce?
C) 0.308 kg*m/s upwards
A plastic block of dimensions 2.00 cm × 3.00 cm × 4.00 cm has a mass of 30.0 g. What is its density?
C) 1.25 g/cm3
A 250-kg motorcycle goes around an unbanked turn of radius 13.7 m at a steady 96.5 km/h. What is the magnitude of the net force on the motorcycle?
C) 1.31x10^4N
A 2.0-kg ball moving eastward at 3.0 m/s suddenly collides with and sticks to a 4.0-kg ball moving northward at 2.0 m/s. What is the magnitude of the momentum of this system just after the collision?
C) 10 kg*m/s
132) An athlete holds a 7.5-kg shot put in his hand with his lower arm horizontal, as shown in the figure. His lower arm has a mass of 2.8 kg and its center of gravity (or center of mass) is 12 cm from the elbow-joint pivot. How much force must the extensor muscle (which is M in the figure) in the upper arm exert on the lower arm?
C) 1000 N
A person weighing 900 N is standing on snowshoes. Each snowshoe has area 2500 cm2 and has negligible weight. What pressure does this person's weight exert on the snow?
C) 1800 N/m2
A 2.0-kg mass moving at 5.0 m/s suddenly collides head-on with a 3.0-kg mass at rest. If the collision is perfectly inelastic, what is the speed of the masses just after the collision?
C) 2.0 m/s
A car traveling at a steady 20 m/s rounds an 80-m radius horizontal unbanked curve with the tires on the verge of slipping. What is the maximum speed with which this car can round a second unbanked curve of radius 320 m if the coefficient of static friction between the car's tires and the road surface is the same in both cases?
D) 40m/s
83) As shown in the figure, a bullet of mass 0.010 kg moving horizontally suddenly strikes a block of wood of mass 1.5 kg that is suspended as a pendulum. The bullet lodges in the wood, and together they swing upward a vertical distance of 0.40 m. The length of the string is 2.0 m. What was the speed of the bullet just before it struck the wooden block?
D) 420 m/s
A dinner plate falls vertically to the floor and breaks up into three pieces, which slide horizontally along the floor. Immediately after the impact, a 200-g piece moves along the +x-axis with a speed of 2.00 m/s, a 235-g piece moves along the +y-axis with a speed of 1.50 m/s. The third piece has a mass of 100 g. What is the speed of the third piece?
D) 5.33 m/s
A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of a circular dive. What is the radius of curvature of the circular part of the path in which the plane is flying
D) 9200m
A spaceship is traveling to the moon. At what point is it beyond the pull of the Earth's gravity?
D) It is never beyond the pull of Earth's gravity.
When is the angular momentum of a system constant?
D) Only when no net external torque acts on the system.
Tensile stress is
D) applied force per cross-sectional area.
A person sits on a freely spinning lab stool that has no friction in its axle. When this person extends her arms,
D) her moment of inertia increases and her angular speed decreases.
Suppose a uniform solid sphere of mass M and radius R rolls without slipping down an inclined plane starting from rest. The linear velocity of the sphere at the bottom of the incline depends on
D) neither the mass nor the radius of the sphere.
An egg falls from a bird's nest in a tree and feels no effects due to the air. As it falls,
D) only its mechanical energy is conserved.
A car goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the car due to the road?
D) perpendicular to the curve inward
When a car is weighed, it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale, and then records a second reading as the rear wheels go over the scale. The weight of the car is equal to
D) the sum of the two weights.
When a car is weighed, it is driven slowly on a horizontal floor over a scale that records a reading as the front wheels go over the scale, and then records a second reading as the rear wheels go over the scale. The weight of the car is equal to A) the weight under the front wheels.
D) the sum of the two weights.
A 1000-kg car is slowly picking up speed as it goes around a horizontal unbanked curve whose radius is 100 m. The coefficient of static friction between the tires and the road is 0.35. At what speed will the car begin to skid sideways?
E) 19 m/s
A batter hits a foul ball. The 0.14-kg baseball that was approaching him at 40 m/s leaves the bat at 30 m/s in a direction perpendicular to the line between the batter and the pitcher. What is the magnitude of the impulse delivered to the baseball?
E) 7.0 N*s
135) As shown in the figure, fluid fills a container having several sections. At which of the indicated points is the pressure greatest?
E) The pressure is the same at each of the labeled points.
Consider a brick that is totally immersed in water, with the long edge of the brick vertical. The pressure on the brick is
E) greatest on the bottom of the brick.
44) In the figure showing an isolated system, determine the character of the collision. The masses of the blocks, and the velocities before and after, are shown. The collision is
E) not possible because momentum is not conserved.
A piece of space debris is released from rest at an altitude that is two earth radii from the center of the earth. Compared to its weight on Earth, the weight of this debris is
E) one-quarter of its weight on the surface of the earth
131) The mobile shown in the figure is perfectly balanced, and the horizontal supports have insignificant masses. What must be the masses of the suspended objects m1, m2, and m3 to maintain balance?
m1 = 1 g m2 = 2 g m3 = 4 g