The weight of the girl is 300 N. The applied force, frictional force, and normal force are all zero. The tension force in the bar is 300 N, and the net force is zero.
The weight of the girl can be calculated using the formula:
Weight = mass × gravity
where mass = 30 kg and gravity = 10 m/s2. Therefore, Weight = 30 kg × 10 m/s2 = 300 N.
Since the girl is motionless, the net force acting on her is zero. In this case, the tension force in the bar equals the weight of the girl, which is 300 N. The other forces (applied force, frictional force, and normal force) are also zero since the girl is not moving.
Therefore, the forces are:
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Explanation :
The gravity of the Sun causes the planets to move in a circular path. This is because of Newton's first law of motion.
According to Newton's first law, the body will remain at rest or in uniform motion untill external unbalanced force acts.
There are two forces acting on planets i.e. gravitational force and inertia of their orbits. So, form Newton's first law the planets keeps on moving in a circular path.
photon?
(1) 1.86 × 10^22 J (3) 4.14 × 10^−19 J
(2) 1.44 × 10^2 J (4) 3.18 × 10^−26 J
Taking into account the definition of photon, energy of a photon, wavelength, frecuency and propagation speed, the correct answer is the option (3): The energy of a photon with aa wavelength of 4.80×10⁻⁷ meter is 4.14×10⁻¹⁹ J.
You have to know that electromagnetic radiation carries energy, which can be absorbed or emitted. To explain the processes of emission and absorption, Plank and Einstein proposed that the energy of radiation is composed of indivisible units (quanta). In each elemental process only a quantum of light can be emitted or absorbed. Each of these quanta was called a "photon".
The exchanges of energy between matter and radiation take place not continuously, but by discrete and indivisible quantities or quanta of energy. The quantum of energy is proportional to the frequency of radiation.
The relationship between the amount of energy (E) transported by the photon and its frequency (f) is determined by the following expression, where the energy of a photon is obtained by multiplying Planck's constant h by the frequency f of electromagnetic radiation:
E=h×f
Wavelength is the minimum distance between two successive points on the wave that are in the same state of vibration. It is expressed in units of length (m).
On the other side, frequency is the number of vibrations that occur in a unit of time. Its unit is s⁻¹ or hertz (Hz).
Finally, the propagation speed is the speed with which the wave propagates in the medium, that is, it is the magnitude that measures the speed at which the wave disturbance propagates along its displacement.
The propagation speed relate the wavelength (λ) and the frequency (f) inversely proportional using the following equation:
v = f×λ
All electromagnetic waves propagate in a vacuum at a constant speed of 3×10⁸ m/s, the speed of light.
In this case, you know:
Replacing in the definition of energy of a photon:
E=h× (v÷λ)
E= 6.63×10⁻³⁴ Js× (3×10⁸ m/s ÷4.80×10⁻⁷ m)
Solving:
E= 4.14×10⁻¹⁹ J
Finally, the correct answer is the option (3): The energy of a photon with aa wavelength of 4.80×10⁻⁷ meter is 4.14×10⁻¹⁹ J.
Learn more about
definition of photon and energy of a photon:
wavelength, frecuency and propagation speed:
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