A. Balloons can be filled with air.
C. Air has mass.
A.gold is the answer. As it's density is 19.32 grams per cubic centimeter which is lot more than the other substances.
Answer:
Here ball and rod will repel each other as they are of similar charges
Explanation:
As we know that the two charges attract or repel each other by electrostatic force
This force is given as

so we know if two charges are similar in nature then they will repel each other and if the two charges are opposite in nature then they will attract each other
So here when rod touch the ball then it transfer its charge to the ball and due to similar charges in ball and rod they both repel each other
Answer:
We know from the basic speed distance relation that

Since the car started from rest and it covered the distance between the 2 officer's in 19 minutes we have speed of the car

Which clearly exceeds the limit of 