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Answer:</h3>
Input work
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Explanation:</h3>
Concept being tested: Efficiency of machines
Therefore we need to know what is the efficiency of a machine
- Efficiency of a machine is the ratio of work output of machine to the work input expressed as a percentage.
Efficiency = (Work output ÷ Work input) × 100%
- Therefore, if the work input is equal to the work output then the efficiency of the machine will be 100%.
- Most machines are not 100% efficient due to loss of energy in form of heat due to friction of the moving parts of the machine.
Voltage= 300V
power= 4500W
Answer and explanation;
In 1670 Gabriel Mouton, Vicar of St. Paul’s Church and an astronomer proposed the swing length of a pendulum with a frequency of one beat per second as the unit of length.
In 1791 the Commission of the French Academy of Sciences proposed the name meter to the unit of length. It would equal one tens-millionth of the distance from the North Pole to the equator along the meridian through Paris.It is realistically represented by the distance between two marks on an iron bar kept in Paris.
In 1889 the 1st General Conference on Weights and Measures define the meter as the distance between two lines on a standard bar that made of an alloy of 90%platinum with 10%iridium.
In 1960 the meter was redefined as 1650763.73 wavelengths of orange-red light, in a vacuum, produced by burning the element krypton (Kr-86).
In 1984 the Geneva Conference on Weights and Measures has defined the meter as the distance light travels, in a vacuum, in 1299792458⁄ seconds with time measured by a cesium-133 atomic clock which emits pulses of radiation at very rapid, regular intervals.
Answer: option b.
Explanation:
The kinetic energy of a spring with constant K is calculated as:
kinetic energy = (k/2)*x^2
Where x^2 is the displacement of the spring with respect to it's rest position.
This can be written as a function like:
x = A*cos(2*pi*f*t)
where:
A is the amplitude (the maximum distance that the spring can move in each direction)
f is the frequency (and 2*pi*f is the angular frequency)
and t is the variable, it represents the time.
Replacing this in the kinetic energy equation, we get:
kinetic energy = (k/2)*(A*cos(2*pi*f*t))^2
This is the same as the option b: b. 1/2kA^2cos^2(2πft)
Then the corrrect option is b.
Answer:
Explanation:
Radius of circular path of coin R = 12.5 x 10⁻²,
coefficient of static friction μs = .33
In order that the coin rotates in circular path , it requires centripetal force which is provided by friction. As speed of rotation increases , force of friction also increases to provide it required centripetal force. When the speed of rotation becomes too high so that frictional force can not compensate the increase in centripetal force then coin will start slipping or it starts moving with respect to turntable.
b ) At this point of time
centripetal force = limiting force of friction
mω² R = μs mg , m is mass of the coin , ω is angular velocity ,
ω² R = μs g
ω² x 12.5 x 10⁻², = .33 x 9.8
ω² = .33 x 9.8 / 12.5 x 10⁻²,
= 25.87
ω = 5.08 rad / s
2π / T = 5.08
T = 2π / 5.08
= 1.23 s .