Answer:
1)
is<u> positive.</u>
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2) 
Explanation:
<h2><u>
Part 1:</u></h2>
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The charged rod is held above the balloon and the weight of the balloon acts in downwards direction. To balance the weight of the balloon, the force on the balloon due to the rod must be directed along the upwards direction, which is only possible when the rod exerts an attractive force on the balloon and the electrostatic force on the balloon due to the rod is attractive when the polarities of the charge on the two are different.
Thus, In order for this to occur, the polarity of charge on the rod must be positive, i.e.,
is <u>positive.</u>
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<h2><u>
Part 2:</u></h2>
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<u>Given:</u>
- Mass of the balloon, m = 0.00275 kg.
- Charge on the balloon,

- Distance between the rod and the balloon, d = 0.0640 m.
- Acceleration due to gravity,

In order to balloon to be float in air, the weight of the balloom must be balanced with the electrostatic force on the balloon due to rod.
Weight of the balloon, 
The magnitude of the electrostatic force on the balloon due to the rod is given by

is the Coulomb's constant.
For the elecric force and the weight to be balanced,

Answer:
18.24 seconds
Explanation:
First you convert the km/h to m/s, 70km/h=(175/9)m/s,85km/h=(425/18)m/s.
You know it took 10 seconds for the police to reach 85 km/h. Calculate the distance that the car is ahead of the police (175/9)*10=1750/9m. Then by divide 1750/9 with 425/18, you will get the value 8.24. Add the 10 seconds with the 8.24 you will get 18.24 sec which is the total time.
The answer is
C. periodic fluctuations in the intensity if sound waves.
For simplicity, let's call vector B-A vector C Then C is
Cx = (-6.1 - 2.2)
Cy = (-2.2 - (-6.9)) Or,
Cx = -8.3 Cy = 4.7
The magnitude is found with the Pythagorean theorem
||C|| = √(-8.3² + 4.7²) = 9.538
Centripetal force = (mv^2)/r
so r = (mv^2)/ force = 246500 / 1100 = 224 m