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3 years ago

What is the average velocity of a car starting from 0 and travels 7 meters in 9 seconds?

Physics

1 answer:

Leni [432]3 years ago

5 0

Your question has been heard loud and clear.

Averge velocity formula= Total distance travelled / total time taken.

Total distance=7meters

Total time taken=9 seconds.

Average velocity = 7/9= 0.77 metres/second

Average velocity= 0.77m/s

Thank you.

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Calculate the energy in the form of heat (in kJ) required to change 75.0 g of liquid water at 27.0 °C to ice at –20.0 °C. Assume

REY [17]

Explanation:

The given data is as follows.

mass, m = 75 g

$T_{1} = 0^{o}C$

$T_{2} = 27^{o}C$

Specific heat of water = 4.18

First, we will calculate the heat required for water is as follows.

q = $m C \times (T_{1} - T_{2})$

= $75 g \times 4.18 J/g^{o}C \times (0 - 27)^{o}C$

= 8464.5 J/mol

= 8.46 kJ ......... (1)

Also, it is given that $T_{3} = -20^{o}C$ = (20 + 273) K = 293 K and specific heat of ice is 2.108 kJ/kg K.

Now, we will calculate the heat of fusion as follows.

q = $mC \times (T_{3} - T_{1})$

= $0.075 kg \times 2.108 kJ/kg K \times (-293 - 0) K$

= -46.32 kJ ......... (2)

Now, adding both equations (1) and (2) as follows.

8.46 kJ - 46.32 kJ

= -37.86 kJ

Therefore, we can conclude that energy in the form of heat (in kJ) required to change 75.0 g of liquid water at $27.0^{o}C$ to ice at $-20.0^{o}C$ is -37.86 kJ.

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3 years ago

What is the energy in joules of a mole of photons associated with visible light of wavelength 486 nm?

Marrrta [24]

Answer:

$2.46\cdot 10^5 J$

Explanation:

The enegy of a single photon is given by:

$E=\frac{hc}{\lambda}$

where

h is the Planck costant

c is the speed of light

$\lambda$ is the wavelength of the photon

In this problem,

$\lambda=486 nm=4.86\cdot 10^{-7}m$

so the energy of one photon is

$E_1=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{4.86\cdot 10^{-7}m}=4.09\cdot 10^{-19} J$

1 mole of photons contains a number of Avogadro of photons:

$N_A = 6.022\cdot 10^{23}$

therefore, the total energy of 1 mole of these photons will be

$E=N_A E_1 = (6.022\cdot 10^{23})(4.09\cdot 10^{-19} J)=2.46\cdot 10^5 J$

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4 years ago

Select all that apply.

FrozenT [24]

The best and most correct answer among the choices provided by the question is peaks and dips .

A transverse wave is characterized by peaks and dips.

Hope my answer would be a great help for you.
If you have more questions feel free to ask here at Brainly.

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3 years ago

A light bulb will glow when electrons flow through it. As the electron flow increases, the brightness increases as well. A stude

Inga [223]

The correct answer is: Unscrew one light, if the others remain on it is a parallel circuit.

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4 years ago

Read 2 more answers

A car with a mass of 500 kg, gets off road and goes straight into a cliff of 30 m with an

mars1129 [50]

Answer:

The velocity of the car when it hits the ground is approximately 55.574 meters per second.

Explanation:

According to this expression, the car goes straight into the cliff and goes down due to gravity, whose situation is described by the Principle of Energy Conservation and supposing that all non-conservative forces are negligible:

$U_{g,1}+K_{1} = U_{g,2}+K_{2}$ (1)

Where:

$U_{g,1}$ , $U_{g,2}$ - Gravitational potential energies of the car at the top and the bottom, measured in joules.

$K_{1}$ , $K_{2}$ - Translational kinetic energies of the car at the top and the bottom, measured in joules.

By definitions of gravitational potential and translational kinetic energies, we expand and simplify the equation above:

$\frac{1}{2}\cdot m\cdot v_{2}^{2} = \frac{1}{2}\cdot m \cdot v_{1}^{2}+m\cdot g \cdot (z_{1}-z_{2})$ (2)

$v_{2}^{2} = v_{1}^{2}+2\cdot g\cdot (z_{1}-z_{2})$

$v_{2} = \sqrt{v_{1}^{2}+2\cdot g\cdot (z_{1}-z_{2})}$

Where:

$m$ - Mass, measured in kilograms.

$v_{1}$ , $v_{2}$ - Velocity of the car at the top and the bottom, measured in meters per second.

$g$ - Gravitaitional acceleration, measured in meters per square second.

$z_{1}$ , $z_{2}$ - Height of the car at the top and at the bottom, measured in meters.

If we know that $v_{1} = 50\,\frac{m}{s}$ , $g = 9.807\,\frac{m}{s^{2}}$ , $z_{1} = 30\,m$ and $z_{2} = 0\,m$ , then the velocity of the car when it hits the ground is:

$v_{2} = \sqrt{\left(50\,\frac{m}{s} \right)^{2}+2\cdot \left(9.807\,\frac{m}{s^{2}} \right)\cdot (30\,m-0\,m)}$

$v_{2}\approx 55.574\,\frac{m}{s}$

The velocity of the car when it hits the ground is approximately 55.574 meters per second.

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3 years ago