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4 years ago

The moons of Mars, Phobos (Fear) and Deimos (Terror), are very close to the planet compared to

Physics

1 answer:

katrin2010 [14]4 years ago

3 0

Answer:D- 0.2528

Explanation:

T=(Rp/Rd)^3/2

T=(9378/23459)^3/2

T=0.2528

The answer is D

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A woman dropped a dime in a wishing well , she heard it 30 sec later ..Find velocity on impact while moving at 9.8 m/s 2

VMariaS [17]

Answer:

The velocity at impact is 222.2 m/s

Explanation:

The given information are;

The time at which the woman heard the sound of the coin after dropping it into the wishing well = 30 seconds

The average speed of sound in air = 344 m/s

The time in which the dime travel = t₁

The time in which the sound travel = t₂

1/2 × 9.8 × t₁² = 344 × t₂

t₁ + t₂ = 30

4.9·t₁² = 344 × (30 - t₁)

4.9·t₁² + 344·t₁ - 10320 = 0

Which gives -344±

$t_1 = \dfrac{-344\pm \sqrt{344^{2}-4\times 4.9 \times 10320}}{2\times 4.9}$

t₁ = 22.676 seconds or -92.9 seconds

Therefore the correct natural time is t₁ = 22.676 seconds

The velocity at impact, v = g×t₁ = 9.8 × 22.676 = 222.2 m/s

The velocity at impact= 222.2 m/s.

8 0

4 years ago

The following table lists the work functions of a few common metals, measured in electron volts. Metal Φ(eV) Cesium 1.9 Potassiu

Citrus2011 [14]

A. Lithium

The equation for the photoelectric effect is:

$E=\phi + K$

where

$E=\frac{hc}{\lambda}$ is the energy of the incident light, with h being the Planck constant, c being the speed of light, and $\lambda$ being the wavelength

$\phi$ is the work function of the metal (the minimum energy needed to extract one photoelectron from the surface of the metal)

K is the maximum kinetic energy of the photoelectron

In this problem, we have

$\lambda=190 nm=1.9\cdot 10^{-7}m$ , so the energy of the incident light is

$E=\frac{hc}{\lambda}=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{1.9\cdot 10^{-7} m}=1.05\cdot 10^{-18}J$

Converting in electronvolts,

$E=\frac{1.05\cdot 10^{-18}J}{1.6\cdot 10^{-19} J/eV}=6.5 eV$

Since the electrons are emitted from the surface with a maximum kinetic energy of

K = 4.0 eV

The work function of this metal is

$\phi = E-K=6.5 eV-4.0 eV=2.5 eV$

So, the metal is Lithium.

B. cesium, potassium, sodium

The wavelength of green light is

$\lambda=510 nm=5.1\cdot 10^{-7} m$

So its energy is

$E=\frac{hc}{\lambda}=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{5.1\cdot 10^{-7} m}=3.9\cdot 10^{-19}J$

Converting in electronvolts,

$E=\frac{3.9\cdot 10^{-19}J}{1.6\cdot 10^{-19} J/eV}=2.4 eV$

So, all the metals that have work function smaller than this value will be able to emit photoelectrons, so:

Cesium

Potassium

Sodium

C. 4.9 eV

In this case, we have

- Copper work function: $\phi = 4.5 eV$

- Maximum kinetic energy of the emitted electrons: K = 2.7 eV

So, the energy of the incident light is

$E=\phi+K=4.5 eV+2.7 eV=7.2 eV$

Then the copper is replaced with sodium, which has work function of

$\phi = 2.3 eV$

So, if the same light shine on sodium, then the maximum kinetic energy of the emitted electrons will be

$K=E-\phi = 7.2 eV-2.3 eV=4.9 eV$

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4 years ago

If the weight of an object that is submerged in a fluid is 10 N and the buoyant force on it is

Nady [450]

Answer: the object should be overcome by buoyancy and rise in the fluid.

Explanation:

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3 years ago

How does a pulley make work easier?

emmasim [6.3K]

it helps use less weight to pick up things and makes it way easier to work

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4 years ago

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What is the ultimate source of energy for an ecosystem?

Romashka-Z-Leto [24]

Answer:

Obviously the answer is Sun...

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3 years ago