MOOC PHYSICS 7C(大学物理1）(大连理工大学)1462480231 最新慕课完整章节测试答案

test 1

1、单选题：
‏ Which of the following is a scalar quantity:‎
选项：
A: speed
B: time
C: length 
D: instantaneous acceleration 
E: instantaneous velocity 
F: average velocity 
G: average acceleration 
H: magnitude of position vector
I: none of the above
答案: 【 speed;
time;
length ;
magnitude of position vector】

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
E: The thumb is x-axis, fingers curled from y-axis to z-axis
F: The thumb is y-axis, fingers curled from z-axis to x-axis
G: none of the above
答案: 【  The thumb is z-axis, fingers curled from x-axis to y-axis;
The thumb is x-axis, fingers curled from y-axis to z-axis;
The thumb is y-axis, fingers curled from z-axis to x-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 sum of 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
E: none of the others
答案: 【 Square root of the sum of squares each A, B and C】

4、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: II
B: I
C: III
D: IV
E: V
F: none of the others
答案: 【 II】

5、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. 

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‍选项：
A: IV
B: I
C: II
D: III
E: V
F: none of the others
答案: 【 IV】

6、单选题：

​The figure shows a position-versus-time graph of the motion of a car. Describe the velocity and acceleration during segments OA, AB, and BC. Which item is Not correct?

‌选项：
A: In segment OA, the velocity is positive and constant.
B: In segment OA, there is no acceleration.
C: In segment AB, the velocity is increasing.
D: In segment AB, there must be acceleration.
E: In segment BC, the velocity is not constant. 
F: In segment BC, this velocity is greater in magnitude than the velocity in segment OA.
答案: 【 In segment BC, the velocity is not constant. 】

7、单选题：
‌A speeder traveling at a constant speed of 100 km/hr passes a waiting police car that immediately starts ‏‌from rest and accelerates at a constant 2.5 m/s^2 How long will it take for the police car to catch the ‏‌speeder?‏‌‏‌‏
选项：
A:  22.2 s
B:  23.3 s
C:  24.8 s
D:  21.4 s
E: 25.1 s
F: 20.2 s
答案: 【  22.2 s】

8、单选题：
A speeder traveling at a constant speed of 100 km/hr passes a waiting police car that immediately starts ​from rest and accelerates at a constant 2.5 m/s^2. How fast will the police car be traveling when it catches the speeder?​‎​
选项：
A:  200 km/hr
B:  210 km/hr
C:  220 km/hr
D:  190 km/hr
E: 180 km/hr
F: 230 km/hr
G: 240 km/hr
答案: 【  200 km/hr】

9、单选题：
‍The acceleration of a bus is given by a(t) =α*t, where α = 1.2 m/s^3. If the bus's velocity at time t = 1.0s is 5.0 m/s, what is its velocity at time t = 2.0 s?‏‍‏‍‏
选项：
A: 6.8 m/s
B: 5.6 m/s
C: 4.5 m/s
D: 7.6 m/s
E: 8.6 m/s
F: 5.1 m/s
G: 5.3 m/s
答案: 【 6.8 m/s】

10、单选题：
‎The acceleration of a bus is given by a(t) =α*t, where α = 1.2 m/s^3. If the bus's position at time t = 1.0 s is 6.0 m, what is its position at time t = 2.0 s?‏‎‏‎‏
选项：
A: 11.8 m
B: 9.5 m
C: 10 m
D: 12.7 m
E: 13.2 m
F: 14.1 m
G: 14.6 m
H: 9.1 m
答案: 【 11.8 m】

Test 2

1、单选题：
‎An object that’s moving with constant speed travels once around a circular path. Which of the following is/are true concerning this 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 only
C: I and III only
D: III only
E: II and III only
F: II only
答案: 【 I only】

2、单选题：
 A rock is thrown off a 30 m cliff at a 45° angle above the horizontal. Which is the following is true regarding the acceleration of the rock? (air resistance is negligible)​​​​
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.
F: None of the others.
答案: 【  The acceleration will be of magnitude g and in a downward direction.】

3、单选题：
‎A 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:  55 m/s
G:  65 m/s
答案: 【 50 m/s】

4、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.
F: None of the others.
答案: 【 The vertical speed decreases on the way up and increases on the way down.】

5、单选题：
‎The position of an object moving in a straight line is given by the equation x = (3t^3 + 7t + 5) m, where t is in seconds. What is the object’s acceleration at time t = 5 seconds?   ________ m/s^2‌
选项：
A: 415 
B: 232
C: 115
D: 90
E: 35
F: 42
G: 230
H: 121
答案: 【 90】

6、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/s^2‏
选项：
A: 0.034
B: 0.0014
C: 1.2
D: 0.87
E: 0.095
F: 0.082
G: 0.23
H: 0.245
答案: 【 0.034】

7、单选题：

​The earth has a radius of 6380 km and turns around once on its axis in 24 h. If  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: 1.4 h
G: 9800 S
H: 6.52 h
I: 8.5h
答案: 【 5070 S ;
1.4 h】

8、单选题：

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

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‏选项：
A: 0.3
B: 0.4
C: 1.0
D: 2.0
E: 3.0
F: 4.0
G: 0.1
H: 5.0
I: 5.3
答案: 【 1.0】

9、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? (Ignore air resistance.)‏
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.】

10、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: 600 mph
C: 357 mph
D: 100 mph
E: 650 mph
F: 450 mph
G: 245 mph
H: 136 mph
答案: 【 357 mph】