大学MOOC College Physics I(Dalian University of Technology)1458264161 最新慕课完整章节测试答案

Pre-course preparation

1、判断题：
‏Velocity in physics is the speed of an object. ‎
选项：
A: 正确
B: 错误
答案: 【 错误】

2、判断题：
‏Acceleration is defined as a vector quantity that indicates the rate of change of velocity.‏
选项：
A: 正确
B: 错误
答案: 【 正确】

3、判断题：
‎Distance and displacement are two quantities that may seem to mean the same thing yet have different definitions and meanings.‏
选项：
A: 正确
B: 错误
答案: 【 正确】

Unit Test 1

1、单选题：
‎Which of the following is a vector quantity:​‎​
选项：
A: speed
B: time
C: acceleration
D: mass
答案: 【 acceleration】

2、单选题：
‍In right handed coordinate system which axis is considered to be positive?​
选项：
A: The thumb is z-axis, fingers curled from y-axis to x-axis
B: The thumb is x-axis, fingers curled from z-axis to y-axis
C: The thumb is y-axis, fingers curled from x-axis to z-axis
D:  The thumb is z-axis, fingers curled from x-axis to y-axis
答案: 【  The thumb is z-axis, fingers curled from x-axis to y-axis】

3、单选题：
​ What is the magnitude of the Cartesian vector having the x, y and z axis components to be A, B and C?‌​‌
选项：
A: Square root of the squares each A, B and C
B:  Square of the squares each A, B and C
C: Cube root of the squares each A, B and C
D: Cube of the squares each A, B and C
答案: 【 Square root of the squares each A, B and C】

4、单选题：
‌The radial component of velocity for a particle moving in a circular path is ______.‌‌‌
选项：
A: A non-zero constant
B:  Radius itself
C: Variable
D: Zero
答案: 【 Zero】

5、单选题：
‏When acceleration is _______, a velocity of a particle is constant.‏‏‏
选项：
A: Constant but non zero
B:  Maximum
C:  Zero
D: None of the above
答案: 【  Zero】

6、单选题：
‏A block sliding down an inclined plane has acceleration _________ acceleration due to gravity.‏‏‏
选项：
A:  Less than
B: Greater than
C:  Same as
D: None of these
答案: 【  Less than】

7、单选题：

‏ A physics professor leaves her house and walks along the sidewalk toward campus. After 5 min it starts to rain and she returns home. Her distance from her house as a function of time is shown in Fig. At Point _________( fill in the labeled points I/ II/ III/ IV/ V) is her velocity zero. 

‌

‏

‌选项：
A: IV
B: I
C: V
D: II
答案: 【 IV】

8、单选题：

‌A physics professor leaves her house and walks along the sidewalk toward campus. After 5 min it starts to rain and she returns home. Her distance from her house as a function of time is shown in Fig. At Point _________( fill in the labeled points I/ II/ III/ IV/ V) is her velocity increasing in magnitude.

​

‌

​选项：
A: IV
B: I
C: V
D: II
答案: 【 II】

9、单选题：
‍A model of a helicopter rotor has four blades, each 3.40 m long from the central shaft to the blade tip. The model is rotated in a wind tunnel at 550 rev/min. The linear speed of the blade tip is ________m/s. ​
选项：
A: 19.6m/s
B: 196m/s 
C: 208m/s 
D:  20.8m/s
答案: 【 196m/s 】

10、单选题：
‏An astronaut has left the International Space Station to test a new space scooter. Her partner measures the following velocity changes, taking place in a 10s interval. At the beginning she is moving toward the right at 15.0 m/s, and at the end she is moving toward the left at 15.0 m/s. The magnitude of her average acceleration is________m/s^2.‍
选项：
A: 3
B: 8
C: 12
D: 7
答案: 【 3】

11、单选题：
‏A body that’s moving with a constant speed travels once around a circular path. Which of the following is/are true concerning the motion?‎‏I. The displacement is zero. II. The average speed is zero. III. The acceleration is zero. ‎‏‎
选项：
A: I only
B: I and II
C: I and III
D:  II and III
E: II only
F: III only
答案: 【 I only】

12、单选题：
‏A rock is thrown off a 35 m cliff at a 45° angle above the horizontal. Which is the following is true regarding the acceleration of the rock? ‎‏‎
选项：
A: The acceleration will be of magnitude g and have both horizontal and vertical components.
B: At the peak of the rock’s path, the magnitude of acceleration will be half of what it was when the rock was initially thrown.
C: The acceleration will be of magnitude g and in a downward direction.
D: The acceleration will be downward during the rock’s ascent and upward during the rock’s descent.
E: The acceleration will increase throughout the rock’s flight.
答案: 【 The acceleration will be of magnitude g and in a downward direction.】

13、单选题：
A small stone is thrown horizontally with an initial speed of 30 m/s from a bridge. Find the stone’s total speed when it enters the water 4 seconds later. (Ignore air resistance.)​
选项：
A: 30 m/s
B: 40 m/s
C: 50 m/s
D: 60 m/s  
E: 70 m/s
F: 80 m/s
答案: 【 50 m/s 】

14、单选题：
‏‍‏Which one of the following statements is true concerning the motion of an ideal projectile launched at an angle of 45°to the horizontal?‍‏‍‏‍
选项：
A: The acceleration vector points opposite to the velocity vector on the way up and in the same direction as the velocity vector on the way down.
B: The speed at the top of the trajectory is zero.
C: The object's total speed remains constant during the entire flight.
D: The horizontal speed decreases on the way up and increases on the way down.
E: The vertical speed decreases on the way up and increases on the way down.
答案: 【 The vertical speed decreases on the way up and increases on the way down.】

15、单选题：
‌The position of an object moving in a straight line is given by the equation x = (3t3 + 7t + 5) m, where t is in seconds. What is the object’s acceleration at time t = 5 seconds?‌‌‌
选项：
A: 415 m/s2 
B: 232 m/s2 
C: 115 m/s2  
D:  90 m/s2 
E: 35 m/s2
答案: 【  90 m/s2 】

16、单选题：
The earth has a radius of 6380 km and turns around once on its axis in 24 h. What is the radial acceleration of an object at the earth’s equator?  _______ m/s2‍‌‍
选项：
A: 0.034
B: 0.0014
C: 1.2
D: 0.87
E: 0.095
答案: 【 0.034】

17、单选题：
‌The earth has a radius of 6380 km and turns around once on its axis in 24 h. If arad at the equator is greater than g, objects will fly off the earth’s surface and into space. What would the period of the earth’s rotation have to be for this to occur?‏‌‏
选项：
A: 5070 S  
B: 8060 S
C: 3.4 h
D: 6080 S
E: 4.6 h  
F: 1.4h  
答案: 【 5070 S  ;
1.4h  】

18、单选题：

‎A ball is projected with an initial velocity of magnitude v0 = 40 m/s toward a vertical wall as shown in the figure. How long does the ball take to reach the wall?______ S

‎

‎ 

‎

‎

‎选项：
A: 0.3
B: 0.4
C: 1.0
D: 2.0
E: 3.0
F: 4.0
答案: 【 1.0】

19、单选题：
‎Two projectiles are launched at 100 m/s, the angle of elevation for the first being 30° and for the second 60°. Which of the following statements is false?‎‎‎
选项：
A: Both projectiles have the same acceleration while in flight.
B: The second projectile has the lower speed at maximum altitude.
C: Both projectiles have the same range.
D: All of the other statements are false.
答案: 【 All of the other statements are false.】

20、单选题：
Plane A is flying at 400 mph in the northeast direction relative to the earth. Plane B is flying at 500 mph in the north direction relative to the earth. What is the speed of Plane B as observed from Plane A?‌‍‌
选项：
A: 900 mph
B: 640 mph
C: 357 mph
D: 100 mph
答案: 【 357 mph】

Pre-course preparation

1、判断题：
‌Equilibrium is the condition of a system when neither its state of motion nor its internal energy state tends to change with time.‏
选项：
A: 正确
B: 错误
答案: 【 正确】

2、判断题：
‍To describe a force, we only need to describe the magnitude that describe "how hard" the force pushes or pulls.​
选项：
A: 正确
B: 错误
答案: 【 错误】

3、判断题：
‍In classical mechanics "kinematics" generally refers to the study of properties of motion-- position, velocity, acceleration. "Dynamics" is the study of the physics of motion and how it relates to applied forces.‌
选项：
A: 正确
B: 错误
答案: 【 正确】

Unit Test 2

1、单选题：
‍Two monkeys of equal mass are holding onto a single vine of negligible mass that hangs vertically from a tree, with one monkey a few meters higher than the other. What is the ratio of the tension in the vine above the upper monkey to the tension in the vine between the two monkeys? ‏‍‏
选项：
A: 2
B: 0.5
C: 1.5
D: More information is required
答案: 【 2】

2、单选题：
​Two blocks, joined by a string, have masses of 6.0 and 9.0 kg. They rest on a frictionless horizontal surface. A 2nd string, attached only to the 9-kg block, has horizontal force = 30 N applied to it. Both blocks accelerate. Find the tension in the string between the blocks.​​​
选项：
A: 12N
B: 22N
C: 18N
D: 25N
答案: 【 12N】

3、单选题：
‍If an object of mass m moves with constant velocity v, the net force on the object is ‏‍‏
选项：
A: mg
B: mv
C: mv/t
D: 0
答案: 【 0】

4、单选题：
‌A large crate of mass m is placed on the back of a truck but not tied down. As the truck accelerates forward with an acceleration a, the crate remains at rest relative to the truck. What force causes the crate to accelerate forward? ‎
选项：
A: the normal force  
B:  the force of gravity 
C: the force of friction between the crate and the floor of the truck 
D: none of these
答案: 【 the force of friction between the crate and the floor of the truck 】

5、单选题：
​​​​If during a given physical process the only force acting on an object is friction, which of the following must be assumed in regard to the object's kinetic energy?​​
选项：
A:  It decreases
B: It increases
C: It remains constant
D: It cannot be determined from the information given
答案: 【 It cannot be determined from the information given】

6、单选题：
‎Which of the following is that form of energy associated with an object's motion?‌‎‌
选项：
A: Potential
B: Thermal
C: Bio-chemical
D: Kinetic
答案: 【 Kinetic】

7、单选题：
‍The work done by static friction can be:​‍​
选项：
A: Positive
B: Negative
C: Zero
D: Any of the others
答案: 【 Any of the others】

8、单选题：
‍The quantity of work equal to one joule is also equivalent to which of the following?‍‍‍
选项：
A: Watt
B: Watt/s
C: Watt∙s
D: Watt /s^2
答案: 【 Watt∙s】

9、判断题：
‍One kilogram of gold would have greater value on Earth than on the Moon.‎‍‎
选项：
A: 正确
B: 错误
答案: 【 错误】

10、判断题：
​An object can move even when no force acts on it. ‌
选项：
A: 正确
B: 错误
答案: 【 正确】

Pre-Course preparation

1、判断题：
Work is a scalar quantity, even though it's calculated by using two vector quantities (force and displacement).  ‏‎‏
选项：
A: 正确
B: 错误
答案: 【 正确】

2、判断题：
Work and power are same thing since both of them involve the amount of energy transferred.‍​‍
选项：
A: 正确
B: 错误
答案: 【 错误】

3、判断题：
Conservation means the preservation of a physical quantity during transformations or reactions.‍‎‍
选项：
A: 正确
B: 错误
答案: 【 正确】

Unit test 3

1、单选题：
‌A boy caught a ball of mass 200g moving with a speed of 30 m/s. If the catching process be completed in 0.1 s, the average net force of impact exerted by the ball on the hands of the boy is‏‌‏
选项：
A:  30N
B: 20N
C: 40N
D: 60N
答案: 【 60N】

2、单选题：
Alex and John are loading identical cabinets onto a truck. Alex lifts his cabinet straight up from the ground to the bed of the truck, whereas John slides his cabinet up a rough ramp to the truck. Which statement is correct about the work done on the cabinet– Earth system?‍‌‍
选项：
A: Alex and John do the same amount of work.
B: Alex does more work than John. 
C: John does more work than Alex. 
D: None of those statements is necessarily true because the angle of the incline is unknown.
答案: 【 John does more work than Alex. 】

3、单选题：
‍A ball of clay falls freely to the hard floor. It does not bounce noticeably, and it very quickly comes to rest. What, then, has happened to the energy the ball had while it was falling? It has been used up in producing the downward motion.‏
选项：
A: It has been used up in producing the downward motion.
B: It has been transformed back into potential energy.
C: It has been transferred into the ball by heat. 
D:  It is in the ball and floor (and walls) as energy of invisible molecular motion.
答案: 【  It is in the ball and floor (and walls) as energy of invisible molecular motion.】

4、单选题：
‍If two particles have equal momenta, are their kinetic energies equal?‎‍‎
选项：
A: yes, always
B: no, never
C: no, except when their speeds are the same
D: yes, as long as they move along parallel lines
答案: 【 no, except when their speeds are the same】

5、单选题：
​An atomic nucleus suddenly bursts apart (fissions) into two pieces. One piece travels off the the left and another piece travels off to the right. The lighter fragment has________speed.‏
选项：
A: greater
B: smaller
C: same
D: an uncertain
答案: 【 greater】

6、单选题：
‍At one instant, the center of mass of a system of two particles is located on the x-axis at x = 2.0 m. One of the particles is at the origin. The other particle has a mass of 0.10 kg and is at rest on the x-axis at x = 8.0 m. The mass of the particle at the origin is          (kg).‌
选项：
A: 0.5
B: 0.3
C: 1.3
D: 1.8
答案: 【 0.3】

7、单选题：
‎I drop a 60-g golf ball from 2.0 m high. It rebounds to 1.5 m. How much energy is lost?‎‎‎
选项：
A: 0.29 J
B: 0.50 J
C: 0.88 J
D: 1.0 J
答案: 【 0.29 J】

8、单选题：
​A girl and her bicycle have a total mass of 40 kg. At the top of the hill her speed is 5.0 m/s. The hill is 10 m high and 100 m long. If the force of friction as she rides down the hill is 20 N, what is her speed at the bottom?​
选项：
A: 5.0 m/s
B: 10 m/s
C: 11 m/s
D: She stops before she reaches the bottom.
答案: 【 11 m/s】

9、单选题：
‌A block is projected with speed v across a horizontal surface and slides to a stop due to friction. The same block is then projected with the same speed v up an incline where is slides to a stop due to friction. In which case did the total mechanical energy of the block decrease the least?‎
选项：
A: This problem cannot be solved since it was not indicated whether the horizontal surface and the incline both had the same coefficient of kinetic friction.
B: The case on the horizontal surface had the least decrease in total mechanical energy.
C: The case on the inclined surface had the least decrease in total mechanical energy.
D: None of the others.
答案: 【 The case on the inclined surface had the least decrease in total mechanical energy.】

10、单选题：
‎Which of the following is an example of a nonconservative force?‍
选项：
A: gravity
B: magnetism
C: friction
D: none of the others
答案: 【 friction】

Pre-course preparation

1、判断题：
​ A body is said to be a rigid body, when it has perfectly definite shape and size. The distance between all points of particles of such a body do not change, while applying any force on it‍
选项：
A: 正确
B: 错误
答案: 【 正确】

2、判断题：
There are 2π radians in one complete revolution.‌‍‌
选项：
A: 正确
B: 错误
答案: 【 正确】

3、判断题：
Torque is a measure of the force that can cause an object to rotate about an axis.‍​‍
选项：
A: 正确
B: 错误
答案: 【 正确】

Unit test4

1、单选题：
‍A grindstone increases in angular speed from 4.00 rad/s to 12.00 rad/s in 4.00 s. Through what angle does it turn during that time interval if the angular acceleration is constant?‏‍‏
选项：
A: 8.00 rad
B: 12.00 rad
C: 16.0 rad
D: 32.0 rad
答案: 【 32.0 rad】

2、单选题：
‏Consider an object on a rotating disk a distance r from its center, held in place on the disk by static friction. Which of the following statements is not true concerning this object?‍‏‍
选项：
A: If the angular speed is constant, the object must have constant tangential speed.
B: If the angular speed is constant, the object is not accelerated.
C: The object has a tangential acceleration only if the disk has an angular acceleration.
D:  If the disk has an angular acceleration, the object has both a centripetal acceleration and a tangential acceleration.
答案: 【 If the angular speed is constant, the object is not accelerated.】

3、单选题：
A constant net torque is exerted on an object. Which of the following quantities for the object cannot be constant? ‎
选项：
A: None of these answers
B: angular acceleration
C: moment of inertia
D: kinetic energy
答案: 【 kinetic energy】

4、单选题：
A solid aluminum sphere of radius R has moment of inertia I about an axis through its center. Will the moment of inertia about a central axis of a solid aluminum sphere of radius 2R be‏‎‏
选项：
A: 2I
B: 4I
C: 8I
D: 32I
答案: 【 32I】

5、单选题：
‏An ice skater starts a spin with her arms stretched out to the sides. She balances on the tip of one skate to turn without friction. She then pulls her arms in so that her moment of inertia decreases by a factor of 2. In the process of her doing so, what happens to her kinetic energy?​
选项：
A:  It increases by a factor of 4.
B:  It increases by a factor of 2.
C:  It decreases by a factor of 2.
D:  It decreases by a factor of 4.
答案: 【  It increases by a factor of 2.】

6、单选题：
‏Consider an isolated system moving through empty space. The system consists of objects that interact with each other and can change location with respect to one another. Which of the following quantities can change in time?​‏​
选项：
A: The angular momentum of the system.
B: The linear momentum of the system.
C: Both the angular momentum and linear momentum of the system.
D: Neither the angular momentum nor linear momentum of the system.
答案: 【 Neither the angular momentum nor linear momentum of the system.】

7、单选题：
‎Two ponies of equal mass are initially at diametrically opposite points on the rim of a large horizontal turntable that is turning freely on a frictionless, vertical axle through its center. The ponies simultaneously start walking toward each other across the turntable.  As they walk, what happens to the angular speed of the turntable?‏
选项：
A:  It increases.
B:  It decreases.
C:  It stays constant.
D: Not Sure
答案: 【  It increases.】

8、单选题：
‎A turntable rotates with a constant 2.25 rad/s^2 angular acceleration. After 4.00 s it has rotated through an angle of 60.0 rad. The angular velocity of the wheel at the beginning of the 4.00s interval was‌‎‌
选项：
A:  10.5 rad/s
B:  19.5 rad/s
C:  14.5 rad/s
D:  17.5 rad/s
答案: 【  10.5 rad/s】

9、单选题：
A solid, uniform cylinder with mass 8.25 kg and diameter 15.0 cm is spinning at 220 rpm on a thin, frictionless axle that passes along the cylinder axis. You design a simple friction brake to stop the cylinder by pressing the brake against the outer rim with a normal force. The coefficient of kinetic friction between the brake and rim is 0.333. What must the applied normal force he to bring the cylinder to rest after it has turned through 5.25 revolutions?‎
选项：
A: 14.9N
B: 24.9N
C: 7.47N
D: 5.47N
答案: 【 7.47N】

10、单选题：
Two particles of different mass start from rest. The same net force acts on both of them as they move over equal distances. How do their final kinetic energies compare?‏
选项：
A: The particle of larger mass has more kinetic energy.
B: The particle of smaller mass has more kinetic energy.
C: The particles have equal kinetic energies.
D:  Either particle might have more kinetic energy.
答案: 【 The particles have equal kinetic energies.】

Pre-course preparation

1、判断题：
Relativity generally refers to two theories of Albert Einstein, his Special Theory of Relativity and his General Theory of Relativity.‌‌‌
选项：
A: 正确
B: 错误
答案: 【 正确】

2、判断题：
Special relativity can not be applied to classical mechanics problems.‍‎‍
选项：
A: 正确
B: 错误
答案: 【 错误】

3、判断题：
Special theory of relativity by Einstein (1905) provides extremely accurate results as long as the domain of study is restricted to large objects and the speeds involved do not approach the speed of light.‎‎‎
选项：
A: 正确
B: 错误
答案: 【 错误】

Unit test5

1、单选题：
In order to reduce your thickness by 40% to an observer at rest, what is the speed with which you must be moving relative to the observer?‏‌‏
选项：
A: 0.8c
B: 0.6c
C: 0.4c
D: 0.2c
答案: 【 0.8c】

2、单选题：
‌To appear to be thin to observers at rest, a young man starts riding a spacecraft. To reduce his thickness exactly by half, the speed at which the spacecraft must move is ‎
选项：
A: 0.5c
B: 0.866c
C: 0.73c
D: 0.95c
答案: 【 0.866c】

3、单选题：
‌In the laboratory frame of reference, the momentum of a particle of rest mass m is found to be 4mc/3  with c the speed of light in vacuum. What is the speed of the particle in the laboratory frame of reference?‌‌‌
选项：
A: 4c/5
B: 3c/5
C: 3c/4
D: c/4
答案: 【 4c/5】

4、单选题：
‍Which statement is correct about the special relativity?‍‍‍
选项：
A: The length has nothing to do with the reference system.
B: The speed of light has nothing to do with the reference system.
C: The mass has nothing to do with the reference system.
D: Time has nothing to do with the reference system.
答案: 【 The speed of light has nothing to do with the reference system.】

5、单选题：
‎A spacecraft zooms past the Earth with a constant velocity. An observer on the Earth measures that an undamaged clock on the spacecraft is ticking at one third the rate of an identical clock on the Earth. What does an observer on the spacecraft measure about the Earth-based clock’s ticking rate?‎
选项：
A:  It runs more than three times faster than his own clock. 
B: It runs three times faster than his own. 
C:  It runs at one-third the rate of his own
D: It runs at less than one-third the rate of his own.
答案: 【  It runs at one-third the rate of his own】

6、单选题：
An astronaut is traveling in a spacecraft in outer space in a straight line at a constant speed of 0.500c. Which of the following effects would she experience?‌‎‌
选项：
A: She would feel heavier.
B: She would find it harder to breathe. 
C: Her heart rate would change.
D: None of those answers is correct.
答案: 【 None of those answers is correct.】

7、单选题：
 A distant astronomical object (a quasar) is moving away from us at half the speed of light. What is the speed of the light we receive from this quasar?‎‌‎
选项：
A: greater than c
B: c
C:  between c/2 and c 
D: c/2 
答案: 【 c】

8、单选题：
‌A spacecraft built in the shape of a sphere moves past an observer on the Earth with a speed of 0.500c. What shape does the observer measure for the spacecraft as it goes by?‎‌‎
选项：
A: a sphere
B: a cigar shape, elongated along the direction of motion 
C: a round pillow shape, flattened along the direction of motion
D: a conical shape, pointing in the direction of motion
答案: 【 a round pillow shape, flattened along the direction of motion】

9、多选题：
As a car heads down a highway traveling at a speed v away from a ground observer, which of the following statements are true about the measured speed of the light beam from the car’s headlights? More than one statement may be correct.‌
选项：
A: The ground observer measures the light speed to be c + v
B:  The driver measures the light speed to be c
C: The ground observer measures the light speed to be c
D: The driver measures the light speed to be c + v
答案: 【  The driver measures the light speed to be c;
The ground observer measures the light speed to be c】

10、多选题：
Which of the following statements are fundamental postulates of the special theory of relativity? More than one statement may be correct.‍‏‍
选项：
A:  Light moves through a substance called the ether. 
B: The speed of light depends on the inertial reference frame in which it is measured. 
C: The laws of physics depend on the inertial reference frame in which they are used.
D: The laws of physics are the same in all inertial reference frames. 
E: The speed of light is independent of the inertial reference frame in which it is measured.
答案: 【 The laws of physics are the same in all inertial reference frames. ;
The speed of light is independent of the inertial reference frame in which it is measured.】

Pre-course preparation

1、判断题：
‍An experiment shows that an electron and a positron can be produced after a high-energy gamma ray collides with a hydrogen atom. This is an experimental evidence for a violation of principle of conservation of charge.‌
选项：
A: 正确
B: 错误
答案: 【 错误】

2、判断题：
‍A test charge is a point charge of a enough small magnitude and it can be either positive or negative.