A small truck has a mass of 2085 kg. How much work is required to decrease the speed of the vehicle from 22.0 m/s to 13.0 m/s on a level road?

Answers

Answer 1

Answer:

Work required is 328387.5 Joules.

Explanation:

Given the following data;

Mass = 2085kg

Initial velocity, Vi = 13m/s

Final velocity, Vf =22m/s

To find the workdone;

We know that from the workdone theorem, the workdone by an object or a body is directly proportional to the kinetic energy possessed by the object due to its motion.

Mathematically, it is given by the equation;

W = Kf - Ki

Where;

W is the work required.

Kf is the final kinetic energy possessed by the object.

Ki is the initial kinetic energy possessed by the object.

But Kinetic energy = ½MV²

W = ½MVf² - ½MVi²

Substituting into the equation, we have;

W = ½(2085)*22² - ½(2085)*13²

Simplifying the equation, we have;

W = 1042.5 * 484 - 1042.5 * 169

W = 504570 - 176182.5

W = 328387.5J

Therefore, the work required to decrease the speed of the vehicle is 328387.5 Joules.


Related Questions

Since the triangle below contains an obtuse angle what type of angle must angle x be

Answers

Answer:

greater than 90 degrees

Explanation:

Two pickup trucks each have a mass of 2,000 kg. The gravitational force between the trucks is 3.00 × 10-5 N. One pickup truck is then loaded with 1,000 kg of bricks. Which of the following would be the new gravitational force between the two trucks?

Answers

Answer:

New gravitational force would be: [tex]4.5\,\,\,10^{-5}\,\,\,N[/tex]

Explanation:

Recall the general form of the gravitational force between two objects of masses m1 and m2 separated a distance "d":

[tex]F_g=G\,\frac{m1\,*\, m2}{d^2}[/tex]

which for the 2000 kg trucks becomes:

[tex]F_g=G\,\frac{m1\,*\, m2}{d^2} \\3\,\,\,10^{-5}\,N=G\,\frac{2000\,*\, 2000}{d^2}[/tex]

when we add 1000 kg of bricks to one truck, we get the following unknown force (x) that we need to find:

[tex]F_g=G\,\frac{m1\,*\, m2}{d^2} \\x=G\,\frac{3000\,*\, 2000}{d^2}[/tex]

Now we divide term by term the last equation by the previous one, in order to cancel out common factors to both equation (G, d^2) and get the following equation:

[tex]\frac{x}{3\,\,\,10^{-5}} =\frac{3000}{2000} \\x=\frac{9}{2} \,10^{-5} =4.5\,\,\,10^{-5}\,\,\,N[/tex]

Plz help I don’t know what to do

Answers

a. compression (the place on a wave where the lines are closest together)
b. rarefaction (the place on a wave where the lines are farthest apart)
c. longitudinal

Suppose we measure the energy stored in some inductor to be E when there is a current I running through it. If I double the current in the inductor, the new total energy will become _____.

a. 8E
b. 2E
c. E
d. E/4
e. E/2
f. 4E

Answers

Answer:

If I double the current in the inductor, the new total energy will become 4E (option f).

Explanation:

The coil or inductor is a passive component made of an insulated wire that stores energy in the form of a magnetic field due to its form of coiled turns of wire, through a phenomenon called self-induction. In other words, inductors store energy in the form of a magnetic field. The energy stored in the space where there is a magnetic field in the inductor is:

[tex]E=\frac{1}{2} *L*I^{2}[/tex]

where E is Energy [J], L is Inductance [H] and I is Current [A].

If you double the current in the inductor, then the new value of the current is I'= 2*I. So replacing the new total energy is:

[tex]E'=\frac{1}{2} *L*I'^{2}=\frac{1}{2} *L*(2*I)^{2}=\frac{1}{2} *L*4*I^{2}=4*\frac{1}{2} *L*I^{2}[/tex]

Then:

[tex]E'=4*E[/tex]

If I double the current in the inductor, the new total energy will become 4E (option f).

[K1 A2 T1 C1] A golfer strikes a golf ball on level ground.

The ball leaves the ground with an initial velocity of 42 m/s [32o

above horizontal].

a. Draw a vector diagram to describe the situation of the of golf

ball with initial velocity.

b. Find the range (horizontal distance) of the golf ball travelled.

c. Find the maximum height (vertical distance) the golf ball

reached.​

Answers

Answer:

Explanation:

See the file attached .

b ) Range of projectile

= u²sin2θ / g

= 42² sin32 x 2 / g

= 42² sin64 / 9.8

= 161.8 m

c )

Max height = u² sin²32 / 2 g

= 42² sin²32 / 2x 9.8

= 25.27  m .

When the displacement of a mass on a spring is 12 A, what percentage of the energy is kinetic energy? At what displacement, as a fraction of A, is the energy half kinetic and half potential?

Answers

Answer:

75%

[tex]\dfrac{A}{\sqrt{2}}[/tex]

Explanation:

x = Displacement of spring = [tex]\dfrac{1}{2}A=\dfrac{A}{2}[/tex]

k = Spring constant

Total energy of the spring is

[tex]E=\dfrac{1}{2}kA^2[/tex]

Elastic potential energy is given by

[tex]U=\dfrac{1}{2}kx^2\\\Rightarrow U=\dfrac{1}{2}k(\dfrac{A}{2})^2\\\Rightarrow U=\dfrac{1}{2}k\dfrac{A^2}{4}\\\Rightarrow U=\dfrac{1}{4}\times \dfrac{1}{2}kA^2\\\Rightarrow U=\dfrac{1}{4}E[/tex]

Total energy is given by

[tex]E=U+K\\\Rightarrow K=E-U\\\Rightarrow K=E-\dfrac{1}{4}E\\\Rightarrow K=\dfrac{3}{4}E\\\Rightarrow \dfrac{K}{E}=0.75[/tex]

The percentage will be

[tex]\dfrac{K}{E}=0.75\times 100\%\\\Rightarrow \dfrac{K}{E}=75\%[/tex]

The required percentage is 75%

According to the given condition

[tex]\dfrac{E}{2}=\dfrac{1}{2}kx^2\\\Rightarrow \dfrac{\dfrac{1}{2}kA^2}{2}=\dfrac{1}{2}kx^2\\\Rightarrow \dfrac{1}{2}kA^2=kx^2\\\Rightarrow x=\sqrt{\dfrac{1}{2}A^2}\\\Rightarrow x=\dfrac{A}{\sqrt{2}}[/tex]

So, the energy is half when displacement is [tex]\dfrac{A}{\sqrt{2}}[/tex]

At 75% ,the energy is kinetic energy.At [tex]\frac{A}{\sqrt{2} }[/tex] a fraction of A, the energy half kinetic and half potential.

Let x be the displacement of spring which is given to be  [tex]\frac{1}{2} A=\frac{A}{2}[/tex]

k= spring constant

Total energy of the spring is:

[tex]E=\frac{1}{2} kA^2[/tex]

Elastic potential energy is given as:

[tex]U=\frac{1}{2} kx^2[/tex]

Now on substituting the value of x in above equation:

[tex]U=\frac{1}{2} k\frac{A^2}{4}[/tex]

It can also be written as:

[tex]U=\frac{1}{4} *\frac{1}{2} kA^2 \\\\U=\frac{1}{4} E[/tex]    (∵[tex]E=\frac{1}{2} kA^2[/tex])

Total energy can be written as:

E=U+K

⇒K=E-U

⇒K=E-1/4 E

⇒K=3/4 E

⇒[tex]\frac{K}{E} =0.75[/tex]

(i) Now, we need to calculate the percentage of kinetic energy:

[tex]\frac{K}{E} =0.75*100=75\%[/tex]

The percentage of kinetic energy is 75%.

(ii) In second it is asked at what displacement, as a fraction of A, is the energy half kinetic and half potential?

∴[tex]\frac{E}{2} =\frac{1}{2} kx^2[/tex]

On substituting the value of E in above equation we will get:

[tex]x=\sqrt{\frac{1}{2} A^2} \\\\x=\frac{A}{\sqrt{2} }[/tex]

So, the energy is half when displacement is [tex]\frac{A}{\sqrt{2} }[/tex] .

Learn more:

brainly.com/question/12337396

A diver makes 0.50 revolutions on the way from a 9.6-m-high platform to the water. Assuming zero initial vertical velocity, find the diver's average angular velocity during a dive.

Answers

Answer:

ω = 0.36 rev/s = 2.24 rad/s

Explanation:

First, we will find the time taken by the diver to reach the water. For this we use 2nd equation of motion:

h = Vi t + (1/2)gt²

where,

h = height = 9.6 m

Vi = initial vertical velocity = 0 m/s

t = time taken = ?

g = 9.8 m/s²

Therefore,

9.6 m = (0 m/s)(t) + (1/2)(9.8 m/s²)t²

t = √1.95 s²

t = 1.4 s

Now, the average angular speed of diver will be:

ω = No. of Revolutions/t

ω = 0.5 rev/1.4 s

ω = 0.36 rev/s = 2.24 rad/s

why did the rocky planets form in the inner section of the solar system

Answers

Answer:

Because it was too hot for volatile compounds (like water) to condense in the inner solar system, rocky planetesimals formed from compounds with high melting points, such as iron and rocky silicates

The tension in a string from which a 7 kg
object is suspended in an elevator is equal to
74 N.

A) What is magnitude of the acceleration a of
the elevator? The acceleration of gravity is
9.8 m/s^2. Answer in units of m/s^2
B) What is its direction?

Answers

Answer:

0.77 m/s^2

Explanation:

Notice that the weight of the 7 kg mass is calculated via:

weight = m * g = 7 * 9.8 N = 68.6 N

Since the tension in the string is larger (74 N), then the elevator is moving upward and the net force on the object is equal to:

74 N - 68.6 N =  5.4 N

Which tells us that the acceleration of the object is:

F = m * a

5.4 N = 7 kg * a

a = 5.4 /7  m/s^2

a = 0.77 m/s^2

and this must be the same as the acceleration of the elevator since object and elevator are moving together.

Which best describes her speed and velocity? (There are 60 seconds in 1 minute.) Her speed is 4.4 m/s, and her velocity is 0 m/s. Her speed is 1.1 m/s, and her velocity is 0 m/s. Her speed is 0 m/s, and her velocity is 2400 m/s. Her speed is 4.4 m/s, and her velocity is 4.4 m/s.

Answers

Answer:

A

Explanation:

Yw :)

Answer:

a

Explanation:

An object is positioned in front of a concave mirror behind the center of curvature. Choose the ray diagram that shows
the proper positioning of the image.

Answers

Answer: it’s the diagram with a small tree on one side and a larger tree on the other side.

The ray diagram that shows the proper positioning of the image is: the first diagram, where the image is smaller than the object.

What is a concave mirror?

A concave mirror also known as converging mirror is a type of curved or spherical mirror in which the outside surface is silvered and the inner surface is made to reflect.

The size and the nature of the image of this kind of mirror is relatively dependent on the position of the object with regards the mirror.

Analysis:

When the object is behind the centre of curvature, the  image is seen to be real, inverted and smaller than the object.

So, the image of the concave mirror increases in size as the object gets closer to the centre of curvature and would be same size as the object at the centre of curvature.

In conclusion, the ray diagram that shows the proper positioning of the image is the first diagram.

Learn more about curved mirrors: brainly.com/question/26257987

#SPJ2

You are out and about in the country and your father sees a rock that he really wants in the yard. Now you must get the very heavy rock into the back of a truck. The truck bed is 3 feet off the ground. Your father pulls out a 5-foot plank and begins to set up a ramp. At the same time, you have found a plank that is 8 feet long, and you show it to your father.


1. Which plank will give you the most mechanical advantage?

Show your step by step work.

Answers

Answer:

The 8ft ramp

Explanation:

L/h

5/3

1.66

1.66:1

L/h

8/3

2.66

2.66:1

8ft is the ramp that would give you the most amount of mechanical advantage.


A disc 28 mm in radius rotates at a constant rate of 1.2 x10^5 rev/hr, about its central axis. Determine the tangential speed at a point 12mm from its center

Answers

Answer:

157m/s

Explanation:

We can convert 1.2 x10^5 rev/hr, to rad/secs for unit consistency

w=1.2×10^5rev/hr ×( 2π rad)/rev ×1 min/60sec

w=13083rad/sec

We can express the tangential speed inform of angular speed

Given speed at a point= 12mm12×10^-3m

V=wr

=13083rad/sec×12×10^-3

=157m/s

Hence the tangential speed at a point 12mm from its center is 157m/s

Name the examples of compounds and their crystalline structure or shape.​

Answers

Answer:

Water - Formula: H2O = Hydrogen2 + Oxygen. ...

Hydrogen Peroxide - Formula: H2O2 = Hydrogen2 + Oxygen2 ...

Salt - Formula: NaCl = Sodium + Chlorine. ...

Baking Soda - Formula: NaHCO3 = Sodium + Hydrogen + Carbon + Oxygen3 ...

Octane - Formula: C8H18 = Carbon8 + Hydrogen18

27.0 mL to the nearest milliliter

Answers

Answer:

27.0 milliliters is the nearest mililiter so 27.0 is the answer

Explanation:

A satellite orbits earth with a mean altitude of 361 km. If the orbit is circular, what are the satellite's time period and speed?

Answers

Answer:

v = 7.69 x 10³ m/s = 7690 m/s

T = 5500 s = 91.67 min = 1.53 h

Explanation:

In order for the satellite to orbit the earth, the force of gravitation on satellite must be equal to the centripetal force acting on it:

[tex]F_{gravitation}= F_{centripetal}\\\\\frac{GM_{s} M_{E}}{r^2} = \frac{M_{s} v^2}{r}\\\\\frac{GM_{E}}{r} = v^2\\\\v = \sqrt{\frac{GM_{E}}{r} } \\\\[/tex]

where,

G = Universal Gravitational Constant = 6.67 x 10⁻¹¹ N.m²/kg²

Me = Mass of Earth = 5.97 x 10²⁴ kg

r = distance between the center of Earth and Satellite = Radius of Earth + Altitude = 6.371 x 10⁶ m + 0.361 x 10⁶ m = 6.732 x 10⁶ m

v = orbital speed = ?

Therefore,

[tex]v = \sqrt{\frac{(6.67 x 10^{-11}N.m^2/kg^2)(5.97 x 10^{24} kg)}{6.732 x 10^6 m} }\\\\[/tex]

v = 7.69 x 10³ m/s

For time period satellite completes one revolution around the earth. It means that the distance covered by satellite is equal to circumference of circle at the given altitude.

So, its orbital speed can be given as:

[tex]v = \frac{Circumference of Circle at Given Altitude}{T}\\\\v = \frac{2\pi r}{T}\\\\[/tex]

where,

T = Time Period of Satellite = ?

Therefore,

[tex]T = \frac{2\pi r}{v}\\\\T = \frac{(2\pi )(6.732 x 10^6 m}{7.69 x 10^3 m/s}\\\\[/tex]

T = 5500 s = 91.67 min = 1.53 h

Planets A and B have the same size, mass, and direction of travel, but planet
A is traveling through space at half the speed of planet B. Which statement
correctly explains the weight you would experience on each planet?
A. You would weigh the same on both planets because their masses
and the distance to their centers of gravity are the same.
O B. You would weigh the same on both planets because your mass
would adjust depending on the planet's speed.
O C. You would weigh less on planet B because it is traveling twice as
fast as planet A.
D. You would weigh more on planet B because it is traveling twice as
fast as planet A

Answers

b , you should weigh the same on both planets because your mass

The explosions that take place during a fireworks show are an example of which of the following?

Image of fireworks exploding in air

Chemical change
Chemical property
Physical change
Physical property

Answers

Answer:

I think it’s the 1rst one chemical change

Explanation:

Answer: A) Chemical Change

Explanation: When a firework explodes it realeses all of its chemical energy, thats why, (A)

is the correct answer

Which of the following elements is more reactive than the

Answers

Answer:

you need to attach a picture so I can answer it

Explain why increasing the mass of a car affects how the car rolls down a ramp.

Answers

F = ma (force = mass x acceleration)

So the car’s mass affects the amount of force, changing how it would roll down a ramp, I think.

Answer:

Q1) Explain why increasing the mass of a car affects how the car rolls down a ramp

Ans1) Weight affects speed down the ramp but it's the mass that affects speed after a car leaves the ramp. Heavier cars have more momentum, so they travel further, given the same amount of friction

Which best describes a metal such as Silver (Ag)?
Group of answer choices

Brittle, a good conductor, and ductile.

Lustrous, malleable, and forms cations.

Dull, highly reactive, and a semiconductor.

Low melting point, forms anions, good insulator.

Answers

Answer:

Brittle, a good conductor, and ductile.

According to the electronic configuration and position of silver in periodic table it can be inferred that it is brittle , good conductor and ductile.

What is electronic configuration?

Electronic configuration is defined as the distribution of electrons which are present in an atom or molecule in atomic or molecular orbitals.It describes how each electron moves independently in an orbital.

Knowledge of electronic configuration is necessary for understanding the structure of periodic table.It helps in understanding the chemical properties of elements.

Elements undergo chemical reactions in order to achieve stability. Main group elements obey the octet rule in their electronic configuration while the transition elements follow the 18 electron rule. Noble elements have valence shell complete in ground state and hence are said to be stable.

Learn more about electronic configuration,here:

https://brainly.com/question/13497372

#SPJ2

7. 100 Joules of work was done to move an object with a force of 15 N. How far did the
object move?

Answers

Answer:Distance=6.67 (rounded)

Explanation: Work = Force x Distance.

100 Joules of work= force of 15 N x Distance (?)

The work equation given above can be rearranged to find force or distance if the other variables are known:

Distance=Work / force

Distance=100Joules/15 N

Distance=6.67 (rounded)

(a) A man stands a distance d = 0.325 m from the left end of a platform as shown in the figure. The platform is supported by three lines. Find the tension in each line (in N). Assume the platform is uniform, with length L = 2.00 m and mass 30.5 kg, and the weight of the man is 675 N. (Due to the nature of this problem, do not use rounded intermediate values in your calculations—including answers submitted in WebAssign.)

Answers

Hi I need a good physics teacher that would help me for a day 123

A bird flies with a constant velocity of 100m/s for 10 minutes. calculate the magnitude of the displacement.​

Answers

Answer:

s = ut

= 100 m/s * 10*60 s

= 60000m

= 60km

Answer:

60 km

Explanation:

velocity (v) = 100m/s

t = 10 minutes = 10(60) = 600 seconds

displacement = velocity × time

s = v × t

s = 100 × 600

s = 60,000m

s = 60,000/1000 km

s = 60km

The fire department arrive to a fire in 210 seconds after leaving the fire station to the burning building which is 840m away. How fast did they travel?

Answers

Answer: The speed is 4 meters per second or 4 m/s.

Explanation:

First, we have the relationship:

Speed = Distance/Time.

In this case, we know that the fire department arrives to a fire in 210 seconds after leaving the fire station to the burning building which is 840m away, this means that:

Time = 210 seconds

Distance traveled in that time = 840m.

Then the speed is:

Speed = 840m/210s = 4 m/s.

The speed is 4 meters per second.

what process resurfaces Venus?

Answers

The catastrophic resurfacing model suggests that planetary resurfacing on Venus occurred through infrequent, planet-wide volcanic events, large enough to bury all earlier material. In other words, resurfacing was a near-instantaneous change to Venus relative to the slow flow of geologic time.

Answer:

Infrequent, planet-wide volcanic events resurface Venus.

Explanation:

An electron (m = 9.1 × 10−31 kg, q = −1.6 × 10−19 C) starts from rest at point A and has a speed of 5.0 × 106 m/s at point B. Only electric forces act on it during this motion. Determine the electric potential difference VA − VB.a) −71 Vb) +71 Vc) −26 Vd) +26 Ve) −140 V

Answers

Answer:

-71 V

Explanation:

Given that,

An electron starts from rest at point A and has a speed of 5.0 × 10⁶ m/s at point B.

We need to find the electric potential difference [tex]V_A-V_B[/tex]. It can be calculated by using the conservation of charges as follows :

[tex]qV=\dfrac{1}{2}mv^2[/tex]

m and q are mass and charge on electrons

[tex]V=\dfrac{mv^2}{2(-q)}\\\\V=-\dfrac{9.1\times 10^{-31}\times (5\times 10^6)^2}{2\times 1.6\times 10^{-19}}\\\\V=-71.09\ V[/tex]

So, the electric potential difference is (-71 V). So, the correct option is (a).

By quadrupling the mass of the body hanging on the thread what will become the period of oscillation?​

Answers

Well, the tension in the thread will probably quadruple, but the hanging body will continue to just hang there.  

The question gives us no evidence that it is doing any oscillating, and there's no reason for it to start just because it suddenly got heavier.

Can u generate energy by impact force? ​

Answers

Answer:

When thinking about the impact force of a falling object, you can calculate the energy of the object at its point of impact if you know the height from which it was dropped.

Explanation:

Which statements describe the types of energy emitted by the Sun? Check all that apply.

It emits most of its energy in gamma rays.
It emits all wavelengths in the electromagnetic spectrum.
It emits most of its energy as visible light.
Its peak wavelength is in the orange-yellow range.
It emits no X-rays or radio waves.
Its peak wavelength is in the yellow-green range.

Answers

The statement that describes the types of energy emitted by the Sun is that It emits all wavelengths in the electromagnetic spectrum, therefore the correct answer is option B.

What is electromagnetic radiation?

Electromagnetic radiation is a type of energy radiation produced by the propagation of electromagnetic waves that are produced for natural as well as anthropogenic reasons.

As given in the problem we have to find out which  statements describe the types of energy emitted by the Sun from the given list of options,

Thus, Sun emits all wavelengths in the electromagnetic spectrum, which means that option B is the appropriate response.

To learn more about electromagnetic radiation, refer to the link ;

brainly.com/question/10759891

#SPJ1

Other Questions
2. How are the circulatory, respiratory and lymphatic systems related to each other? specific. Zara ate 75 almonds this week, or 150% as many as she ate last week. How many almonds did Zara eat last week? The percent written as a part-to-whole ratio is to 100. 150 divided by is equal to 75. 100 divided by is equal to . Zara ate almonds last week. How can governments both harm and help there people? Which innovation gave the Sumerians an advantage in war? BronzeIrrigationCuneiformIron A graph has minutes on the x-axis and ounces of popcorn on the y-axis. A curve goes through points (0, 0), (50, 12), and (110, 18).Rachel had a popcorn machine at her party. Determine whether the relationship between time and the amount of popcorn popped is directly proportional.Yes, for every 10 minutes there were 4 ounces of popcorn popped.Yes, the input is time and the output is the amount of popcorn popped.No, the graph does not make a straight line.No, the graph does not go through the origin. Mi gato ____________ temprano (desalination) Match each moon or planet to the most accurate characteristic.A. Earth's moon B. Venus C. Europa D. Mars 1. It contains large amounts of frozen water 2. The temperature of its atmosphere is increased by high levels of carbon dioxide 3. It doesn't have enough gravity to have an atmosphere 4. Astronomers believe there is a good chance it contains liquid water what event typically causes upwelling? What do the actions of the lion say about the relationship between love and identity? What were the three main causes of the Industrial Revolution? (in Britain)PLEASE NO COPY PASTING FROM GOOGLE i truly need help. 1. Human to ____Human____2. _Human________ to machine3. Machine to ______Machine4. _______________ to machine Hello! Can anyone please tell me the measurement of t and v ? Any help is gladly appreciated. Can somebody help me wit this ? Cause Ion understand this . Where should a comma be inserted in the sentence?My long-legged shaggy-haired dog bounded downthe twisting trail after me.A. after dogB. after twistingC. after long-leggedD. after shaggy-haired Juan plans to build a bookcase to store his paperback books, DVDs, and CDs. He has lumber that he will use for the sides and the back of the bookcase. The bookcase will have five shelves, and each will be 2 1/2 long.Does he have enough lumber to make the five shelves? Reread the last stanza of John Montague's poem "The Fight". (p.20)For minutes we foughtStanding and falling inThe rivers brown spate.And I would still fight,Though now I can forgive;To worship or destroy beautyThat double edge of the impulseI recognize, by which we live:But also the bitter paradoxOf betraying love to harm,Then lunging, too late,With fists, to its defense.How is this stanza different from the rest of the poem? 6 - (-7) =Subtract integers using inverse property. Jamison owns a rental cabin in Mammoth, and travels there for maintenance three times a year, between January and June. The round trip to Mammoth from San Diego where Jamison lives, is approximately 405 miles. How much travel costs can Jamison deduct per year related to his rental cabin?a. $248b. $686c. $743d. $1,352 Which option describes a gas-liquid solution?A) a liquid solute evaporated into a gas that then acts as a solventb) a liquid solute dissolved in a gaseous solventc) a gaseous solute dissolved in a liquid solventd)a gaseous solute condensed into a liquid that then acts as a solvent According to the synthetic division below, which of the following statements are true? Check all that apply.