The velocity of the board relative to the ice is zero, since both are at rest.
<h3>What is relative velocity?</h3>
Relative velocity is the velocity of an object in relation to another reference object or point.
When two objects are travelling or moving with the same velocity in the same direction, the relative velocity one relative to the other is zero.
Also, when two objects are at rest, the relative velocity one relative to the other is zero.
Therefore, the velocity of the board relative to the ice is zero, since both are at rest.
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Tapping means the maximum use of the energy by the people.
<h3>What is energy?</h3>
The energy is the ability to do work.
The energy that can be tapped is solar energy. There are many ways developed to tap the solar energy and make the best use of it by solar plant, water heating, cooking, etc.
Thus, tapping means the maximum use of the energy by the people.
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Answer:
The ratio of electric force to the gravitational force is 
Explanation:
It is given that,
Distance between electron and proton, 
Electric force is given by :

Gravitational force is given by :

Where
is mass of electron, 
is mass of proton, 
is charge on electron, 
is charge on proton, 



So, the ratio of electric force to the gravitational force is
. Hence, this is the required solution.
Answer : The value of the constant for a second order reaction is, 
Explanation :
The expression used for second order kinetics is:
![kt=\frac{1}{[A_t]}-\frac{1}{[A_o]}](https://tex.z-dn.net/?f=kt%3D%5Cfrac%7B1%7D%7B%5BA_t%5D%7D-%5Cfrac%7B1%7D%7B%5BA_o%5D%7D)
where,
k = rate constant = ?
t = time = 17s
= final concentration = 0.0981 M
= initial concentration = 0.657 M
Now put all the given values in the above expression, we get:


Therefore, the value of the constant for a second order reaction is, 
120 minutes=2 hours
20/2= 10mph