Answer:
f =1 10⁸ Hz
Explanation:
The speed of an electromagnetic wave is given by
c = Lam f
In our case, the wavelength is 3.0 m, so we can clear the frequency
f = c / Lam
f = 3 108/3.
f =1 10⁸ Hz
Answer: The correct answer is option B.
Explanation:
Mass of the sled = 10 kg
Initial speed of the sled = 2 m/s
Kinetic energy of the sled = 

Work done by the sled = 20 joules
The work done by the friction will be in opposite direction and equal to the magnitude of the work done of the sled that - 20 J.
Hence, correct answer is option B.
Answer:
For cast iron we have

For copper

For Lead

For Zinc

Explanation:
As we know that final speed of the block is calculated by work energy theorem

now we have

now we have


For cast iron we have


For copper


For Lead


For Zinc


Option D is correct. An arch carries the thrust of weight to its <u>sides </u>with a <u>post-and-lintel.</u>
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<h3>What is an arch?</h3>
An arch is indeed a vertical curving construction that covers an elevated space that may or may not sustain the load above it or the pressure gradient against it
In the case of a horizontally arched, such as an embankment dam. While arches and vaults are often confused, A vault is defined as an ongoing arch forming a roof.
Option D satisfies the fill-in blanks option.
Hence option D is correct. An arch carries the thrust of weight to its <u>sides </u>with a <u>post-and-lintel.</u>
<u></u>
To learn more about the arch refer to the link;
brainly.com/question/18162421