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Sholpan [36]
3 years ago
11

An ice cube is placed in a microwave oven.

Physics
1 answer:
Juli2301 [7.4K]3 years ago
5 0

Answer:

It takes 266 seconds to melt the ice.

Explanation:

Given data

  • Power of the microwave oven (P): 125 Watt
  • Heat supplied to the ice (Q): 33,200 Joule
  • Time for the melting (t): to be determined

In order to determine the time required to melt the ice, we can use the following expression.

P = Q/t

t = Q / P = 33,200 J/ 125 W = 266 s

It takes 266 seconds to melt the ice.

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The Atwood’s machine shown consists of two blocks of mass m1 and m2 that are connected by a light string that passes over a pull
Talja [164]

(A) For the system consisting of the two blocks, the change in the kinetic energy of the system is equal to work done by gravity on the system.

(D) For the system consisting of the two blocks, the pulley and the Earth, the change in the total mechanical energy of the system is zero.

<h3 /><h3>The given parameters:</h3>
  • Mass of block 1 = m1
  • Mass of block 2, = m2
  • Height of block 1 above the ground, = h1
  • Height of block 2 above the ground = h2

The total initial mechanical energy of the two block system is calculated as follows;

m_1gh_1 + \frac{1}{2} m_1v_1_i^2 = m_2gh_2 + \frac{1}{2} m_2v_2_i^2\\\\m_1gh_1 + 0 = m_2gh_2 + 0\\\\m_1gh_1 = m_2gh_2\\\\m_1gh_1 - m_2gh_2 = 0

When the block m2 reaches the ground the block m1 attains maximum height and the total mechanical energy at this point is given as;

m_1g(h_1 + h_2) + K.E_1 = \frac{1}{2}m_2v_{max}^2 + P.E_2\\\\m_1g(h_1 + h_2 ) -PE_2 = \frac{1}{2}m_2v_{max}^2 - K.E_1\\\\m_1g(h_1 + h_2 )  - 0= \frac{1}{2}m_2v_{max}^2 - 0\\\\m_1g(h_1 + h_2 )  = \frac{1}{2}m_2v_{max}^2\\\\W = \frac{1}{2}m_2v_{max}^2

Thus, we can conclude the following before the block m2 reaches the ground;

  • For the system consisting of the two blocks, the pulley and the Earth, the change in the total mechanical energy of the system is zero.
  • For the system consisting of the two blocks, the change in the kinetic energy of the system is equal to work done by gravity on the system.

Learn more about conservation of mechanical energy here: brainly.com/question/332163

5 0
3 years ago
‏Explain how an electron emitted by the photoelectric effect can have kinetic energy less than threshold energy ?
xenn [34]

Answer:

the photons (quanta of light) collide with the electrons, these electrons have to overcome the threshold energy that is the energy of union with the metal, and the energy that remains is converted to kinetic energy.

          K = E - Ф

Explanation:

The photoelectric effect is the emission of electrons from the surface of a metal.

This was correctly explained by Einstein, in his explanation the energy of the photons (quanta of light) collide with the electrons, these electrons have to overcome the threshold energy that is the energy of union with the metal, and the energy that remains is converted to kinetic energy.

          E = hf

          E = K + Ф

          K = E - Ф

The energy of the photons is given by the Planck relation E = hf and according to Einstein the number of joints must be added

            E = n hf

Therefore, depending on the value of this energy, the emitted electrons can have energy from zero onwards.

4 0
3 years ago
The bonds of oxygen molecules are broken by sunlight. The minimum energy required to break the oxygen-oxygen bond is 495 kJ/mol.
makvit [3.9K]

Answer:

The wavelength of sunlight that can cause this bond breakage is 242 nm

Explanation:

The minimum energy of the sunlight that'll break Oxygen-oxygen bond must match 495 KJ/mol

But 1 mole of any molecule contains 6.02 × 10²³ molecules/mol

Each molecule of Oxygen will require (495 × 10³)/(6.02 × 10²³) = 8.22 × 10⁻¹⁹ J

E = hf

v = fλ

f = v/λ

f = frequency of the sunlight

λ = wavelength of the sunlight

v = speed of light = 3.0 × 10⁸ m/s

E = hv/λ

λ = hv/E

h = Planck's constant = 6.63 × 10⁻³⁴ J.s

λ = (6.63 × 10⁻³⁴)(3 × 10⁸)/(8.22 × 10⁻¹⁹)

λ = 2.42 × 10⁻⁷ m = 242 nm.

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