Notes

Question 1
(1 points)

{#720482) {Vector Dot Product}



Consider the two vectors shown in the figure below (figure not drawn to scale).



Vector A has a magnitude of
∣
�
⃗
∣
=
∣
​A
​⃗
​​ ∣= 13.2

m
e
t
e
r
s
meters

Vector B has a magnitude of
∣
�
⃗
∣
=
∣
​B
​⃗
​​ ∣= 5.11

m
e
t
e
r
s
meters

and the two vectors make an angle of
�
�
�
=
θ
​AB
​​ = 36.0

d
e
g
r
e
e
s
degrees



Calculate the value of the dot product :
�
=
�
⃗
⋅
�
⃗
c=
​A
​⃗
​​ ⋅
​B
​⃗
​​





Image size: SMLMax



Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8
54.6
m
2
m
​2
​​
Your Answer
Your actual answer was 54.56 which differs from the answer above by a small rounding error or significant figures. Check with your instructor how this will be graded in a testing situation.
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Question 2
(1 points)

(9934497) {Work}



What is the S.I. unit for work?

Select the correct answer
newtons (N)
kg-meters per sec (kg m /s)
watts (W)
meters per sec (m/s)
joules (J)
Your Answer
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Question 3
(1 points)

(038155) {Work}



If you exert a force on an object, but the object remains stationary as you apply the force, then how much work have you done on the object?



Select the correct answer
an amount that is greater than zero
zero work was done on the object
Your Answer
an amount that is less than zero
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LAST ATTEMPT!

Question 4
(1 points)

(966534) {Work}



Which of the following is the most accurate definition of work?

Select the correct answer
rate at which an object is moved
force acting over distance moved perpendicular to the direction of the force
force acting over distance
Your Answer
force acting over distance moved in the same direction as the force
force acting over time
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Question 5
(1 points)

(4486985) {Work}



Julie is holding a 5 kg book 1 m above the ground, Bob is holding a 10 kg book 2 m above the ground and Anna is holding a 7.5 kg book 1 m above the ground. All three students hold their book steady without moving for 5 minutes. Rank from greatest to least the amount of work being done by each person during this 5 minute period. (use > to indicate one value is greater than another, use = to indicate they are the same.)

Select the correct answer
work(Bob) = work(Anna) = work (Julie)
work(Bob) > work(Anna) > work (Julie)
work(Bob) > work(Anna) = work (Julie)
work(Julie) > work(Anna) > work (Bob)
work(Bob) > work(Julie) > work (Anna)
No answer submitted
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Question 6
(1 points)

(602931) {Conservation of Energy}



What is the basic concept underlying the principle of conservation of energy?

Select the correct answer
energy cannot be created or destroyed
what goes up must come down
energy can never be transferred from one object or system to another object or system.
energy cannot change from one type of energy to another
always take the easy path
No answer submitted
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Question 7
(1 points)

(9934497) {Kinetic Energy}



Suppose a cart is moving without any loss of energy to friction or air resistance. As the cart passes under a bridge, a heavy block is dropped vertically downward onto the cart from a very small height above the cart. What happens to the speed of the cart?

Select the correct answer
The speed of the cart remains the same as before the block was dropped on it.
The cart will either speed up or slow down depending on whether the block is lighter or heavier than the cart.
The speed of the cart is now faster than before the block was dropped on it.
The speed of the cart is now slower than before the block was dropped on it.
No answer submitted
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Question 8
(1 points)

(176490) {Kinetic Energy}



Consider two boxes of masses, m and 2m, both initially at rest. You push each box separately with a force, F, over a distance ,d, across a frictionless surface. How does the final kinetic energy of the lighter box compare to the final kinetic energy of the larger box.

Select the correct answer
the kinetic energy of the lighter box is greater than the kinetic energy of the heavier box.
the kinetic energy of the lighter box is smaller than the kinetic energy of the heavier box.
the kinetic energy is the same for both boxes.
No answer submitted
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Question 9
(1 points)

(057856) {Kinetic Energy}



Olympic gold medalist Usain Bolt can run
1
0
0
m
100m in roughly
1
0
s
10s, and his mass is roughly
1
0
0
k
g
100kg. A powerful rifle bullet moves at roughly
1
0
0
0
m
/
s
1000m/s and has a mass of approximately
1
0
g
10g. Let
�
U
s
a
i
n
K
​Usain
​​ denote Usain Bolt's approximate kinetic energy, and let
�
b
u
l
l
e
t
K
​bullet
​​ be the bullet's approximate kinetic energy. Which of the following is true according to these rough figures?

Select the correct answer
�
U
s
a
i
n
=
�
b
u
l
l
e
t
K
​Usain
​​ =K
​bullet
​​
�
U
s
a
i
n
>
�
b
u
l
l
e
t
K
​Usain
​​ >K
​bullet
​​
�
U
s
a
i
n
<
�
b
u
l
l
e
t
K
​Usain
​​ <K
​bullet
​​
No answer submitted
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Question 10
(1 points)

(321301) {Gravitational Potential Energy}



Galileo releases a ball at the top of a building. What can be said about the potential energy at the top and the kinetic energy right before impact with ground? Ignore the effects of air resistance.

Select the correct answer
Potential energy at top > kinetic energy just before impact
It cannot be determined
Potential energy at top < kinetic energy just before impact
Potential energy at top = kinetic energy just before impact
No answer submitted
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Question 11
(1 points)

(632224) {Gravitational Potential Energy}



A hydroelectric power facility converts the gravitational potential energy of water behind a dam into electric energy. Consider a lake of volume
5
0
.
0

k
m
3
50.0 km
​3
​​ (
m
a
s
s
=
5
.
0
0
×
1
0
1
3

k
g
mass=5.00×10
​13
​​ kg). Assume that the water extends from the height of the generators to 80.0 m above them so that the average height of the water is 40.0 m above the generators. What is the gravitational potential energy of the lake if we take the zero of gravitational potential energy to be at the level of the generators?



Select the correct answer
3
.
3
3
×
1
0
1
5

J
3.33×10
​15
​​ J
1
.
5
0
×
1
0
1
4

J
1.50×10
​14
​​ J
2
.
7
8
×
1
0
1
8

J
2.78×10
​18
​​ J
1
.
9
6
×
1
0
1
6

J
1.96×10
​16
​​ J
8
.
2
5
×
1
0
1
6

J
8.25×10
​16
​​ J
No answer submitted
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Question 12
(1 points)

(079183) {Gravitational Potential Energy}



The bicep curl is an exercise where you lift up a barbell with weights attached by bending of your arms at the elbow. Assume your forearm length (elbow to hand) is 0.557 m, and the barbell is lifted by a vertical distance that is twice the forearm length. Also assume that the barbell is at rest at both the start and the end of the motion. Calculate how much energy it take to curl a barbell with a total weight of 49.8 lb?

Image size: SMLMax



Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
J
No answer submitted
0 of 5 checks used

Question 13
(1 points)

(272649) {Gravitational Potential Energy}



A child with a mass of 29.1 kg sits in a sled at the top of a hill that is 19.3 m high. Assuming no energy is lost to friction as the child slides down hill, what is the child's kinetic energy at the bottom of the hill?

Select the correct answer
2.77e+3
J
4.48e+3
J
2.23e+3
J
5.50e+3
J
3.28e+3
J
No answer submitted
0 of 3 checks used

Question 14
(1 points)

(428409) {Gravitational Potential Energy}



The UCSD annual Watermelon Drop started in the spring of 1965 in Revelle College . The 1965 Watermelon Drop Queen, Elizabeth Heller, flung a 
1
0
�
�
10kg watermelon off of the seventh floor (height 
2
0
�
20m) of Urey Hall with initial vertical speed of 
4
�
/
�
4m/s . What's the velocity before the watermelon just hit on the ground? Let's practice this question in two different ways: (1) Kinematic equation you learned previously. (2) Energy conservation you learned in this chapter. You should arrive at the same result by either method.



Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
m/s
No answer submitted
0 of 5 checks used

Question 15
(1 points)

(876225) {Gravitational Potential Energy}



A 0.232 kg toy car moves across a flat surface with an initial speed of 12.9 m/s. It then moves up a inclined plane with an angle of 36.7 degrees above horizontal. What is the speed of the car after it has moved 1.91 m along the plane?

Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
m/s
No answer submitted
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Question 16
(1 points)

(610600) {Spring Potential Energy}



The force required to slowly stretch a spring varies from 0 N to 204 N as the spring is extended by 15 cm from its unstretched length. What is the force constant of the spring?

Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
N/m
No answer submitted
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Question 17
(1 points)

(653667) {Spring Potential Energy}







The potential energy of a particular mass-spring system is 10 J when the spring is stretched by a distance of A. What is the potential energy when the same mass-spring system when the spring is only stretched by a distance of A/2 ?

Select the correct answer
7.5 J
5 J
20 J
2.5 J
6.7 J
10 J
No answer submitted
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Question 18
(1 points)

(170829) {Spring Potential Energy}



A
4
.
7
4
×
1
0
5

k
g
4.74×10
​5
​​ kg subway train is brought to a stop from a speed of 1.22 miles per hour in 0.436 m by a large spring bumper at the end of its track. What is the force constant k of the spring?

Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
N/m
No answer submitted
0 of 5 checks used

Question 19
(1 points)

(117539) {Spring Potential Energy}



Consider a mass-spring system. The spring has a spring constant of 1.49e+3 N/m. On the end of the spring is a mass of 1.01 kg. At the moment that the block is at the system's equilibrium position, it has velocity of 2.96 m/s. What will be the maximum displacement of the block from equilibrium if we ignore all friction.

Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
m
No answer submitted
0 of 5 checks used

Question 20
(1 points)

(67325) {Spring Potential Energy}



You compress a spring with a spring constant of 988 N/m by 0.944 m, and then place a 0.969 kg mass next to the compressed spring. Upon release, the spring pushes the mass across a frictionless table surface. What is the maximum velocity the mass achieves?

Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
m/s
No answer submitted
0 of 5 checks used

Question 21
(1 points)

(2445638) {Spring Potential Energy}



Assume that the force of a bow on an arrow behaves like the spring force. In aiming the arrow, an archer pulls the bow back 35.6 cm and holds it in position with a force of 157 N. If the mass of the arrow is 50 g and the “spring” is considered to be massless, what is the speed of the arrow immediately after it leaves the bow?





Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
m/s
No answer submitted
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Question 22
(1 points)

(972291) {Spring Potential Energy}



The massless spring of a spring gun has a force constant of
�
=
1
2
0
0

N
/
m
k=1200 N/m and is compressed by a distance, d. When the gun is aimed vertically, a 24.2-g projectile is shot to a maximum height of 5.0 m above the original height of the projectile, as shown in the figure below. Calculate the distance, d, that the spring was initially compressed.

Image size: SMLMax



Please enter a numerical answer below. Accepted formats are numbers or "e" based scientific notation e.g. 0.23, -2, 1e6, 5.23e-8

Enter answer here
meters
No answer submitted
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