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2 years ago

Where does energy originate ina food web

Physics

2 answers:

Vesnalui [34]2 years ago

6 0

Answer:

In a food web the energy is originated through the sun or star.

ValentinkaMS [17]2 years ago

4 0

$\huge{\underline{\underline{\red{Answer}}}}$

In a food web the energy is originated from the SUN.

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A 1990 kg car moving at 20.0 m/s collides and locks together with a 1540 kg car at rest at a stop sign. Show that momentum is co

Ilya [14]

Answer:

The momentum before collision and momentum after collision is equal in a frame of reference moving at 10.0 m/s in the direction of the moving car.

Explanation:

$m_1$ = Mass of moving car = 1990 kg

$u_1$ = Velocity of moving car in stationary frame = 20 m/s

$m_2$ = Mass of stationary car = 1540 kg

$u_2$ = Velocity of stationary car in stationary frame = 0 m/s

v = Combined velocity in stationary frame

Momentum conservation for stationary frame

$m_1u_1+m_2u_2=(m_1+m_2)v\\\Rightarrow v=\dfrac{m_1u_1+m_2u_2}{m_1+m_2}\\\Rightarrow v=\dfrac{1990\times 20+0}{1990+1540}\\\Rightarrow v=\dfrac{3980}{353}\ \text{m/s}$

In frame moving at 10 m/s the velocities change in the following ways

$u_1=20-10\\\Rightarrow u_1=10\ \text{m/s}$

$u_2=0-10\\\Rightarrow u_1=-10\ \text{m/s}$

$v=\dfrac{3980}{353}-10\\\Rightarrow v=\dfrac{450}{353}\ \text{m/s}$

Momentum before collision

$m_1u_1+m_2u_2=1990\times 10+1540\times -10\\\Rightarrow m_1u_1+m_2u_2=4500\ \text{kg m/s}$

Momentum after collision

$(m_1+m_2)v=(1990+1540)\times \dfrac{450}{353}\\\Rightarrow (m_1+m_2)v=4500\ \text{kg m/s}$

The momentum before collision and momentum after collision is equal. So, the momentum is conserved in a reference frame moving at 10.0 m/s in the direction of the moving car.

7 0

3 years ago

If I spacecraft seems to be Motionless in deep space is given some type of quick push what will happen

Pavlova-9 [17]

Newtons 3rd law of motion states the every action has an equal and opposite reaction, so in space with no gravity and no friction the ship would move in what ever direction it was pushed forever, until it would reach some kind of gravitational pull.

Hope this was right, =]
JT

3 0

2 years ago

A photoelectric effect experiment finds a stopping potential of 1.93 V when light of wavelength 200 nm is used to illuminate the

PSYCHO15rus [73]

a) zinc

The equation of the photoelectric effect is:

$E=\phi + K$ (1)

where

E is the energy of the incident light

$\phi$ is the work function

$K$ is the maximum kinetic energy of the emitted photoelectrons

Here the wavelength of the incident light is

$\lambda=200 nm = 2\cdot 10^{-7} m$

so the energy of the light is

$E=\frac{hc}{\lambda}=\frac{(6.63\cdot 10^{-34} Js)(3\cdot 10^8 m/s)}{2\cdot 10^{-7} m}=9.95\cdot 10^{-19} J$

Converting into electronvolts,

$E=\frac{9.95\cdot 10^{-19}}{1.6\cdot 10^{-19} J/eV}=6.22 eV$ (2)

The stopping potential is the potential needed to stop the photoelectrons with maximum kinetic energy: so, the electrical potential energy corresponding to the stopping potential (V=1.93 V) must be equal to the maximum kinetic energy of the photoelectrons,

$U=q V = K$

and since the charge of the electron is

1 q = 1 e

We have

$K=(1 e)(1.93 V)=1.93 eV$ (3)

Combining (1), (2) and (3), we find the work function of the material:

$\phi = E-K=6.22 eV-1.93 eV=4.29 eV$

So, the cathode is most likely made of zinc, which has a work function of 4.3 eV.

b) The stopping potential does not change

As we said in part A), the stopping potential is proportional to the maximum kinetic energy of the photoelectrons, K.

The intensity of light is proportional to the number of photons that hit the surface of the metal. However, the energy of these photons does not depend on the intensity, but only on the frequency of the light.

Therefore, the energy of the photons (E) does not change when the intensity of light is doubled. Also, the work function $\phi$ does not change: this means that the maximum kinetic energy of the photoelectrons, K, does not change, and so the stopping potential remains the same.

6 0

3 years ago

HOLA, NECESITO AYUDA!

givi [52]

The electrostatic force between the two ions is $2.9\cdot 10^{-10} N$