The answer is A because An Indicator" changes color when it comes in contact with an acid or a base
An indicator could be anything like:
1) Litmus paper
2) Bromothymol blue
3) Phenolphthalein
Answer:
Explanation:
Given
mass of boy 
mass of girl 
speed of girl after push 
Suppose speed of boy after push is 
initially momentum of system is zero so final momentum is also zero because momentum is conserved




i.e. velocity of boy is 2.82 m/s towards west
Answer:
because when squeezing you are increasing pressure within the bottle and there is less pressure on the outside
Answer:

Explanation:
The total charge is distributed over the two objects:

The plate and the rod must have
. So the charge transferred from the plate to the rod is:

Number of electrons:

So that we do not contaminate it with microorganisms or garbage or other human stuff.