Answer: The control group is the part where you see what happens when you change a variable you want to study/examine. Basically, you need the control group because you need something to see what happens when you change something.
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Transverse Waves: Displacement of the medium is perpendicular to the direction of propagation of the wave. ... Longitudinal Waves: Displacement of the medium is parallel to the direction of propagation of the wave.
The answer is A. Hope this helps I tried my best!
Answer : The speed of waves along the wire is, 1.2 m/s
Explanation :
Formula used :

where,
= frequency = 
= wavelength =
c = speed of wave = ?
Now put all the given value in the above formula, we get the speed of waves along the wire.


Thus, the speed of waves along the wire is, 1.2 m/s
Answer:
The size of the hole will increase
Explanation:
Heat is a form of energy that depends to a great extent on the temperature of the system,when a solid is heated there will be increases in it's length,area and volume otherwise known as linear,beta and superficial expansivities respectively.When Annette increased the temperature of the ring she supplied heat to the ring that led to the expansion of the ring,what really happened was that she increased the area expansivities of the ring which is the increase in area per unit area per degree rise in temperature,at such the interior diameter of the ring increase to such an extent that the ball passes through it.