Three runners are competing in a 120-m race. Each begins when the starting signal sounds and all three runners cross the finish line at the same time. The first runner moves at a constant speed of 6 m/s. The second runner sprints at a constant speed of 7.5 m/s, stops after 60 m to rest for 4 s, then runs the second half of the race at a constant speed of 7.5 m/s. The third runner dashes 60 m at a constant speed of 12 m/s but realizes they forgot their keys, so runs back to the starting line at a constant speed of 12 m/s, then turns around and runs straight to the finish line at a constant speed of 12 m/s. Which of the following statements about this situation is NOT true?
Assume all average velocities and average speeds are for the period from the starting signal to the moment the runners cross the finish line. You may select more than one option.
a. The average speed of the third runner is not equal to his average velocity
b. The average velocity of the third runner is zero.
c. The first runner's average velocity is equal to the second runner's average velocity
d. The second runner's average speed is less than 7.5 m/s.
e. All three runners have the same average velocity.

Answer: 490

Explanation:

Answer:

One source of carbon dioxide is us.

Explanation:

we inhale oxygen and exhale carbon dioxide.

One significant source of carbon dioxide emissions is the combustion of fossil fuels. When fossil fuels like coal, oil, and natural gas are burned for energy, they release carbon dioxide into the atmosphere.

The combustion process involves the reaction of fossil fuels with oxygen, resulting in the release of carbon dioxide as a byproduct.  

For example, when gasoline is burned in a car's engine, it undergoes combustion, producing carbon dioxide along with other combustion byproducts. Similarly, when coal is burned in a power plant to generate electricity, it emits carbon dioxide into the atmosphere.

These human activities, particularly the burning of fossil fuels, have significantly increased the concentration of carbon dioxide in the Earth's atmosphere.

However, human activities are the primary drivers of the increased levels of carbon dioxide in the atmosphere over the past century.

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Answer:

Since the wire is not splitting at any point in the circuit,

the resistors are in series

Hence, Equivalent resistance = 10 + 20 + 30

Equivalent Resistance = 60 Ω

Explanation:

the rate at which something occurs or is repeated over a particular period of time or in a given sample

Answer:

Frequency is the number of occurrences of a repeating event per unit of time. It is also referred to as temporal frequency, which emphasizes the contrast to spatial frequency and angular frequency. Frequency is measured in units of hertz (Hz) which is equal to one occurrence of a repeating event per second.

Hope this helps :D

Answer:

total distance travelled

Explanation:

Answer:

Scientists learn about the layers deep within the Earth's crust by studying how seismic waves travel through the Earth. ... By looking at the time of arrival of the main set of waves, and how the frequencies of the waves are arranged within the set, scientists can learn about the density and other properties of the layers.

Explanation:

Just read above.

Answer:

a) If both are charged

b) the first team has a load and the second half of it

c) The first team has a charge contrary to the rod, it is charged by induction and the second team has a charge equal to the rod, it is charged by contact

Explanation:

For this exercise let's analyze the charge on each electroscope separately

electroscope 1

Suppose the student with her finger on the device is grounded,

When bringing the rod closer to the electroscope a charge is indexed, on the side of the rod on the opposite side there is the same charge but with the opposite sign, as the student is grounded, this charge passes to the ground, this side remains neutral.

When removing the finger, loads can no longer pass, and when removing the rod the load from this side distributes throughout the equipment, therefore it has a load of the same magnitude as the rod

Electroscope 2

In this case, the equipment is touched, so the load redistributes in the two, when separating it remains with half the load of the cheek.

After analyzing each device separately we can answer the questions.

a) If both are charged

b) the first team has a load and the second half of it

c) The first team has a charge contrary to the rod, it is charged by induction and the second team has a charge equal to the rod, it is charged by contact

Answer:

this is my old profile,i just need my back

Answer:

Explanation:

The diagram showing the illustration of the question is shown on the first uploaded image

Here G represents the base

So the displacement in the x -axis is mathematically represented as

[tex]X = 11200 + 8400 = 19600 \ m[/tex]

The displacement in the y -axis is mathematically represented as

[tex]Y 3200 + 1700 = 4900 \ m[/tex]

Generally the resultant displacement is

[tex]R = \sqrt{ X^2 + Y^2}[/tex]

[tex]R = \sqrt{ 19600^2 + 4900^2}[/tex]

[tex]R = 20200\ m [/tex]

Generally the direction of this resultant displacement is mathematically represented as

[tex]\theta = tan ^{-1} [\frac{Y}{X} ][/tex]

=>       [tex]\theta  =  tan ^{-1} [\frac{4900}{19600} ][/tex]

=>            [tex]\theta  = 14.03 ^o  [/tex]

Hence the direction is  [tex]14.03 ^o[\tex] from the horizontal axis

Answer:

the  wavelength of the wave is 1.5 m

Explanation:

Given;

speed of the wave, v = 90 m/s

frequency of the wave, f = 60 Hz

The wavelength of the wave is given as;

v = fλ

λ = v / f

where;

λ is the wavelength of the wave

Substitute the given values of v and f, to determine the wavelength.

λ = v / f

λ = 90 / 60

λ = 1.5 m

Therefore, the  wavelength of the wave is 1.5 m

Answer:

79.29

Explanation:

Given that,

The y component of a vector, y = 36

The angle between the vector and the x-axis is 27.

We need to find the magnitude of a vector.

Let a and b are x and y component of a vector m. There resultant is R. So,

[tex]R=\sqrt{a^2+b^2}[/tex]

Where

[tex]a=c\cos\theta\ \text{and}\ b=c\sin\theta[/tex]

We have, b = 36 and θ = 27°

So,

[tex]36=R\sin\theta\\\\R=\dfrac{36}{\sin\theta}\\\\R=\dfrac{36}{\sin(27)}\\R=79.29[/tex]

So, the magnitude of the vector is 79.29

Answer: hope it helps

We routinely share first-person accounts of what we've seen or heard ... Accidental eyewitnesses to daily events, ranging from the mundane ... System variables, by contrast, are those that can be controlled by the ... Comparing the diagnostic accuracy of suspect identifications made by actual eyewitnesses ...

Explanation:

Answer:

34

Explanation:

Answer:

Velocity=-0.033

Speed=0.17

Explanation:

Answer:

(472i + 80.3j) m

Explanation:

Given the following :

Distance of tee shot = 300m

Distance of second shot = 189.0 m

Displacement r1 of tee shot :

r1 = 300 mi

Displacement r2 of second shot :

r2 = 172.0 mi + 80.3 mj

The final displacement of the golf ball from the tee:

r_final = r1 + r2

r_final = (300i)m + (172.0i + 80.3j) m

r_final = (300 + 172)i m + 80.3j m

r_final = (472i + 80.3j) m

Answer:

b) 31.4 m^2

Explanation:

Area of rectangle = lb

= 4.79 x 3.547

= 16.990

Approximately 17m²

A¹ = pi(d/2)²

= Pi(6.32m/2)²

= 31.37m

=Approximately 31.4

31.4 m² is the most precise estimate that you can obtain from your measurements for the area of your bedroom

Answer: the answer is b

Explanation:

Answer:

true

Explanation:

Answer:

ask questions about the

Explanation:

Answer:

SI unit of density - Kilogram per cubic metre (Kg/m³)

CGS unit of density - gram per cubic centimetre (g/cm³)

The question is missing some parts. Here is the complete question.

An ideal gas is contained in a vessel at 300K. The temperature of the gas is then increased to 900K.

(i) By what factor does the average kinetic energy of the molecules change, (a) a factor of 9, (b) a factor of 3, (c) a factor of [tex]\sqrt{3}[/tex], (d) a factor of 1, or (e) a factor of [tex]\frac{1}{3}[/tex]?

Using the same choices in part (i), by what factor does each of the following change: (ii) the rms molecular speed of the molecules, (iii) the average momentum change that one molecule undergoes in a colision with one particular wall, (iv) the rate of collisions of molecules with walls, and (v) the pressure of the gas.

Answer: (i) (b) a factor of 3;

              (ii) (c) a factor of [tex]\sqrt{3}[/tex];

              (iii) (c) a factor of [tex]\sqrt{3}[/tex];

             (iv) (c) a factor of [tex]\sqrt{3}[/tex];

              (v) (e) a factor of 3;

Explanation: (i) Kinetic energy for ideal gas is calculated as:

[tex]KE=\frac{3}{2}nRT[/tex]

where

n is mols

R is constant of gas

T is temperature in Kelvin

As you can see, kinetic energy and temperature are directly proportional: when tem perature increases, so does energy.

So, as temperature of an ideal gas increased 3 times, kinetic energy will increase 3 times.

For temperature and energy, the factor of change is 3.

(ii) Rms is root mean square velocity and is defined as

[tex]V_{rms}=\sqrt{\frac{3k_{B}T}{m} }[/tex]

Calculating velocity for each temperature:

For 300K:

[tex]V_{rms1}=\sqrt{\frac{3k_{B}300}{m} }[/tex]

[tex]V_{rms1}=30\sqrt{\frac{k_{B}}{m} }[/tex]

For 900K:

[tex]V_{rms2}=\sqrt{\frac{3k_{B}900}{m} }[/tex]

[tex]V_{rms2}=30\sqrt{3}\sqrt{\frac{k_{B}}{m} }[/tex]

Comparing both veolcities:

[tex]\frac{V_{rms2}}{V_{rms1}}= (30\sqrt{3}\sqrt{\frac{k_{B}}{m} }) .\frac{1}{30} \sqrt{\frac{m}{k_{B}} }[/tex]

[tex]\frac{V_{rms2}}{V_{rms1}}=\sqrt{3}[/tex]

For rms, factor of change is [tex]\sqrt{3}[/tex]

(iii) Average momentum change of molecule depends upon velocity:

q = m.v

Since velocity has a factor of [tex]\sqrt{3}[/tex] and velocity and momentum are proportional, average momentum change increase by a factor of

(iv) Collisions increase with increase in velocity, which increases with increase of temperature. So, rate of collisions also increase by a factor of [tex]\sqrt{3}[/tex].

(v) According to the Pressure-Temperature Law, also known as Gay-Lussac's Law, when the volume of an ideal gas is kept constant, pressure and temperature are directly proportional. So, when temperature increases by a factor of 3, Pressure also increases by a factor of 3.

Answer:

hago

Explanation:

hago mis quehaceresmeans means I do my homework

Answer:

a. 50.9 mΩ b. 9.32 × 10¹⁸ electrons/s c. 4.55 × 10⁵ A/m² d. i. resistance and current density  ii. They would decrease.

Explanation:

a. The resistance of the copper wire is given by

R = ρl/A where ρ = resistivity of copper wire = 1.68 × 10⁻⁸ Ωm, l = length of copper wire = 10 m and A = cross-sectional area of coper wire = πd²/4 where d = diameter of copper wire = 2.05 mm = 2.05 × 10⁻³ m

A =  πd²/4  

= π(2.05 × 10⁻³ m)²/4

= 13.2025/4  × 10⁻⁶ m²

= 3.3 × 10⁻⁶ m².

So R = ρl/A

=  1.68 × 10⁻⁸ Ωm × 10 m/3.3 × 10⁻⁶ m²

= 0.0509 Ω

= 50.9 mΩ

b. Since a current of 1.5 A flows through the wire, it means that 1.5 C/s, that is 1.5 Coulombs of charge flows through it per second.

Since 1 electron = 1.609 × 10⁻¹⁹ C, the number of electrons in 1.5 A is 1.5 C/s ÷ 1.609 × 10⁻¹⁹ C per electron = 1.5/1.609 × 10⁻¹⁹ C = 9.32 × 10¹⁸ electrons/s

c. The current density J = I/A where I = current = 1.5 A and A = cross-sectional area of copper wire = 3.3 × 10⁻⁶ m²

J = 1.5 A/3.3 × 10⁻⁶ m²

= 4.55 × 10⁵ A/m²

d. i. If the diameter were twice the initial diameter, d' = 2d, then the resistance and current density would change since they are dependent of the cross-sectional area of the wire which is then dependent on the diameter of the wire.

ii. If the diameter were twice the initial diameter, d' = 2d, then since the cross-sectional area A' = πd'²/4 = π(2d)²/4 = 4πd²/4 = 4A. So, the cross-sectional area increases by a factor of four.

The new resistance R' =  ρl/4A = R/4

The new current density J' = I/4A = J/4.

So the resistance and current density would decrease.

Well, to begin with, your first number gang somewhat aglay. The land speed record that John Howard set on his bicycle in 1985 was 152.2 miles per hour, which works out to 68.04 m/s. So I can see where you got the 6 and the 8 from, but your little decimal point snuck over one place when you weren't looking.

I'll use your number to answer the question. If my solution turns out to be wrong, then it's because you copied the number wrong, and you'll have to work it out again with an initial speed of 68.1m/s.

Initial speed = 6.81 m/s

Final speed = 5.44 m/s

Amount of slowing down = 1.37 m/s

Rate at which the brakes slow you down = 3 m/s each second

Time needed to slow down 1.37 m/s = (1.37 m/s) / (3 m/s^2)

That's 0.457 second. (obviously absurd)

If initial speed = 68.1 m/s

Then amount of slowing down = 62.66 m/s

Time needed at -3 m/s^2 = (62.66/3)

That's 20.9 seconds. Much more reasonable.

By the way, John Howard's record was broken 10 yrs later, in 1995 .

Time  it will take for the bicycle’s speed to decrease to 5.44 m/s is 20.9 seconds.

The speed of an object is the magnitude of the change of its position over time or the magnitude of the change of its position per unit of time; it is thus a scalar quantity.

Given

Initial speed = 6.81 m/s

Final speed = 5.44 m/s

Amount of slowing down = 1.37 m/s

Rate at which the brakes slow you down = 3 m/s each second

Time needed to slow down 1.37 m/s = (1.37 m/s) / (3 m/s^2)

That's 0.457 second. (obviously absurd)

If initial speed = 68.1 m/s

Then amount of slowing down = 62.66 m/s

Time needed at -3 m/s^2 = (62.66/3)

Time  it will take for the bicycle’s velocity to decrease to 5.44 m/s is 20.9 seconds.

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Answer:

yes SI units are used for scientific works

Explanation:

because they are standard units and can be used by anyone easly

Answer:

 Δt = 3.04 10³ s

Explanation:

a) This is a thermal conduction exercise that is described by the expression

         P = k A | dT/dx |     (1)

where P power, k thermal  conductivity, A the area, T the temperature and x the thickness

The power supplied to the wood is

          P = Q / Δt

where the heat is given by

         Q = m [tex]c_{e}[/tex] ΔT'

we substitute

         P = m c_{e} ΔT'/ Δt

We assume that the changes in temperature and time can be approximated by their differences,

we substitute in 1

          m c_{e} ΔT'/Δt = k A dT / dx

as the temperature changes are small, we can assume a linear variation, consequently the derivatives can be approximated to the variations

           m ce ΔT'/Δt = k A ΔT/Δx    (2)

let's write the temperature variations explicitly

        ΔT’= (T_f -T₀)

        ΔT’= 56 -0

        ΔT = [tex](T_{h} - T_{c} )[/tex]

        ΔT = 70 -0    

the thermal diffusivity is

           α = k /ρ c_{e}

            k = α c_{e}

the definition of density

            ρ = m / V

            ρ = m / A L

            k = α c_{e} m / A L

we substitute   in 2

          m c_{e} Δx = (α c_{e} m / A L) A ΔT /ΔT'   dt

          Δx = α /L   ΔT / ΔT’  Δt

          Δt = L Dx /α ΔT'/ΔT

let's calculate

          Δt = 2.54 1.27 10⁻⁴ / 8.5 10⁻⁸    (56- 0) / (70-0)

          Δt = 3.04 10³ s

Answer:

The value is  [tex]KE = 9 J[/tex]

Explanation:

From the question we are told that

      The mass is  [tex]m = 0.5 \ kg[/tex]

     The velocity is  [tex]v = 6 \ m/s[/tex]

Generally the kinetic energy is mathematically represented as

        [tex]KE = \frac{ 1}{2} * m*v^2[/tex]

=>     [tex]KE = \frac{ 1}{2} * 0.5*6^2[/tex]

=>     [tex]KE = 9 J[/tex]

Answer:

well at the rate he goes he would be at 2.5km