Answer:
1)
is<u> positive.</u>
<u></u>
2) 
Explanation:
<h2><u>
Part 1:</u></h2>
<u></u>
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>
<u></u>
<h2><u>
Part 2:</u></h2>
<u></u>
<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,

<span>Subrahmanyan Chandrasekhar
</span>
Explanation:
<em>Two</em><em> </em><em>factors</em><em> </em><em>that</em><em> </em><em>affect</em><em> </em><em>the</em><em> </em><em>rater</em><em> </em><em>of</em><em> </em><em>diffusion</em><em> </em><em>of</em><em> </em><em>a</em><em> </em><em>substance</em><em> </em><em>are</em><em>:</em><em> </em>
- <em>Diffusion</em><em> </em><em>of</em><em> </em><em>substance</em><em> </em><em>plays</em><em> </em><em>an</em><em> </em><em>important</em><em> </em><em>role</em><em> </em><em>on</em><em> </em><em>cellular</em><em> </em><em>transport</em><em> </em><em>in</em><em> </em><em>plants</em><em>.</em><em> </em>
- <em>Diffusion</em><em> </em><em>is</em><em> </em><em>the</em><em> </em><em>passive</em><em> </em><em>movement</em><em> </em><em>of</em><em> </em><em>substance</em><em> </em><em>from</em><em> </em><em>a</em><em> </em><em>region</em><em> </em><em>of</em><em> </em><em>higher</em><em> </em><em>concentration</em><em> </em><em>to</em><em> </em><em>a</em><em> </em><em>region</em><em> </em><em>of</em><em> </em><em>lower</em><em> </em><em>concentration</em><em>. </em>
Answer:
1) t=1.743 sec
2)Vo=61.388 m/sec
3)the x component of its velocity just be- fore it strikes the ground is the same as the initial velocity of the ball that is=61.388 m/sec
4)Vf=17.08 m/s
Explanation:
1)From second equation of motion we get
h=Vit+(1/2)gt^2
here in case(a): Vi=0 m/s,h=14.9m,,put these values in above equation to find the time the ball is in motion
14.9=(0)*t+(1/2)(9.8)t^2
t^2=14.9/4.9
t^2=3.040 sec
t=1.743 sec
2) s=Vo*t
Putting values we get
107=Vo*1.743
Vo=61.388 m/sec
3)the x component of its velocity just be- fore it strikes the ground is the same as the initial velocity of the ball that is=61.388 m/sec
4)From third equation of motion we know that
Vf^2-Vi^2=2gh
here Vi=0 m/s,h=14.9 m
Vf^2=Vi^2+2gh=0+2(9.8)(14.9)
Vf^2=292.04
Vf=17.08 m/s