Answer:
Velocity, v = 0.239 m/s
Explanation:
Given that,
The distance between two consecutive nodes of a standing wave is 20.9 cm = 0.209 m
The hand generating the pulses moves up and down through a complete cycle 2.57 times every 4.47 s.
For a standing wave, the distance between two consecutive nodes is equal to half of the wavelength.

Frequency is number of cycles per unit time.

Now we can find the velocity of the wave.
Velocity = frequency × wavelength
v = 0.574 × 0.418
v = 0.239 m/s
So, the velocity of the wave is 0.239 m/s.
Answer:
Time will be 19 ms so option (a) is correct option
Explanation:
We have given that mass of wire m = 50 gram = 0.5 kg
Frequency f = 810 Hz
Wavelength = 0.4 m
Velocity is given by

Amplitude is given as d = 6 m
So time 
So option (a) is correct option
Answer: A) Wavelength and frequency are inversely proportional.
Explanation:
From the wave equation;
Velocity= frequency × wavelength
If the above equation is rearranged making the frequency the subject of formula, it would give;
Frequency= velocity/ wavelength.
From the above equation we see that frequency is inversely proportional to the wavelength. This means that for every increase in wavelength there would be a decrease in frequency, and for every increase in frequency there is a reduction in wavelength.
<u>Answer:</u>
For a. Neutrons and electrons also form an atom.
For b. The element is oxygen which is a non-metal and will form a negative ion while forming ionic bond.
<u>Explanation:</u>
There are 3 subatomic particles which form an atom. These are neutrons, protons and electrons.
Neutrons carry no charge, protons carry positive charge and electrons carry negative charge. Neutrons and protons are present in nucleus and electrons revolve around the nucleus.
The energy which is present between neutrons and protons are nuclear energy and the energy which is present between electrons and protons are electrostatic energy.
In an element, number of protons is always equal to the number of electrons. The atomic number is equal to the number of protons or electrons. The element which has atomic number 8 is Oxygen.
The electronic configuration of this element is 
This element requires only 2 electrons to form a stable electronic configuration. An element which gains electron is considered as a non-metal and forms a negative ion because number of electrons increases.
Answer:
Explanation:
1- Density increase as the temperature decreases. This is the reason why liquid water is more dense than solid water.
2- The only things that affect the period of a simple pendulum are its length and the acceleration due to gravity.
3- not really sure for that one...I will think about that.
4- same reason for number 3