Answer:
The correct option is 80 dB.
Explanation:
The transformation of sound intensity level into sound intensity utilizes the formula
[D] = 10 log (I/I₀)
Where I₀ = 10⁻¹² W/m²
[D] results in 100 dB
100 = 10 log (I/I₀)
Log (I/I₀) converts to 10
(I/I₀) = 10¹⁰
I is determined as I₀ × 10¹⁰ = 10⁻¹² × 10¹⁰ = 10⁻² W/m²
Sound intensity inversely relates to the square of the distance from the source.
I ∝ (1/d²)
I can be expressed as k/d²
When d = 1 m, the intensity is 10⁻² W/m²
Thus, 0.01 = k/1
Providing that k = 0.01 W
For d = 20 m, we can calculate I
I = 0.01/20² = 2.5 × 10⁻⁵ W/m²
With four neighbors mowing their lawns concurrently,
I = 4 × 2.5 × 10⁻⁵ = 10⁻⁴ W/m⁻²
The sound intensity level in decibels is represented as
[D] = 10 log (I/I₀)
[D] = 10 log (10⁻⁴/10⁻¹²)
[D] = 10 log (10⁸)
[D] = 10 × 8 = 80dB
Factors influencing friction
The magnitude of friction is contingent on the following elements: i) The surface area in contact. ii) The applied pressure on the surfaces. Force is determined by Pressure multiplied by Area; thus, if the contact area increases or if the pressure applied rises, the frictional force will also escalate.
Methods for reducing friction
i) Smooth the contact surface. ii) Apply oil or grease to fill small gaps in flat surfaces. iii) Use ball bearings to minimize contact area among rotating components.
Lubrication
To minimize friction, various methods may be employed: Oil can be either thin or viscous, which depends on its SAE number (SAE indicating Society of Automotive Engineers). Highly viscous oils may not reach all components effectively. In contrast, very thin oils may drain away quickly, resulting in wastage. Grease is preferable in such situations, particularly around ball-bearings. Regular grease or oil should not be utilized under high speed, high pressure, and high temperature conditions—specialized lubricants are required then. The consistency of oil varies with temperature; it thickens in the cold and thins in the heat. Therefore, the choice of lubricant should be seasonally appropriate, and it's always wise to consult the equipment's operating manual prior to making a selection.[[TAG_11]]
The star is moving away from our planet. To elaborate on the Doppler shift: This phenomenon, related to the Doppler effect, is the variation in the perceived frequency or wavelength (color) of a wave when the source of the waves and the observer are in motion relative to one another. Consequently, it can be inferred that as an object recedes, it exhibits more redshift in its spectrum. For instance, when a star moves away, its spectral lines shift towards the red end of the spectrum, whereas if it approaches Earth, the spectral lines move towards blue. Given that the peak wavelength is roughly 650 nm—which is associated with red—it can be concluded that the star is indeed moving away from Earth.
Answer:
a)9.8
Explanation:
because any object falling from any height experiences 9.8
(sorry that's all I know)
The formula used is known as the Law of Universal Gravitation. The gravitational constant G is 6.67×10⁻¹¹ Nm²/kg². The Earth's mass is <span>5.972 ×10</span>²⁴ kg. The mass of the rocket is negligible in comparison to Earth’s mass, hence it is unnecessary for our calculations. Plugging in the values:
F = (6.67×10⁻¹¹ Nm²/kg²)(5.972 ×10²⁴ kg)/(4000 miles*(1.609 km/1 mile))²
F = 9616423.08 N
The work done is given by
W = Fd
W = (9616423.08 N)(2000 miles*1.609 km/mile)
W = 9.095×10¹⁰ Joules
