1bt this is d q nw help
a particle havin +ve chrge is releasd frm rest in eltric field and moves under d influence of both d eltric field n gravity .wich of d follwon qunatites conncted wid d chrged particle continously increases wid tym
Eltric potenial enrgy
gravitational potential enrgy
eltric chrge
kinctic enrgy
it will depnd on d dirction of eltric field na ??
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13 Answers
1yeah i noe ....n thats rite .bt they shud hav had also specified d dirction na '
'?
106@ subash. suppose the particle was moving with velocity v initially. Let the electric field and gravitational field be opposite in direction and the corresponding forces be F and G respectively .. If F and G resultant is opposite to body's velocity then KE decreases otherwise it increases. If the resultant is perpendicular then KE remains constant.. In other cases u need to take components. Hence all the above mentioned quantities if they increase or decrease will depend on the magnitude as well as direction..
11I don't think any carged particle in it's right mind wud go in the direction of increasing electric potential energy.....this will happen only if the particle was negatively charged.....but it's given that the particle has positive charge so we can rule out (a)
we can rule out (b) as well because no particle will go in the direction of increasing gravitational potential energy
charge doesn't depend on any other parameter so (c) is not the answer
the particle moves from higher potential energy to lower potential energy..........this decrease in potential energy translates to gain in kinetic energy
106@ani consider this situation.
particle of charge 2C and mass 2kg.. Gravitational field = 3N/kg Electric field = 5N/C and initial speed = 2m/s in direction indicated
The forces on the particle are grav. force = 6N (right) and electric force = 10N (left)
Hence there is retardation and hence KE decreases. In this situation particle moves opposite to grav. field hence grav. PE increases and Elec. PE increases as the particle moves in the direction of field.
U = qV = q(-∫E.dr) = -q(∫Edr) (as E and dr are in same direction) hence U <0 If Grav force was greater in mag. than electric force then grav PE wud have been -ve and electric PE increasing.
There can also be many situations where the fields are not collinear and both PE increase or both decrease
106Anirudh_872: hey, asish
Anirudh_872: in that example that u gave
9:54
Anirudh_872: Electric force is greater than gravitational force right?
Anirudh_872: so the particle will move in the direction of electric field
asish_1069: yes
asish_1069: yes
Anirudh_872: so how are E and dr in opposite drections?
9:56
asish_1069: ur rite
asish_1069: edited
asish_1069: :P
9:58
Anirudh_872: there will be a battle of potential energies
Anirudh_872: whatever wins, the particle WILL move in a direction of decreasing potential energy
9:59
Anirudh_872: and by potential energy i mean net potential energy
10:0
asish_1069: yes but the options are not net PE they are separate for grav PE and elec. PE
Anirudh_872: yup
Anirudh_872: that's the problem
Anirudh_872: but whatever increases or decreases, the kinetic energy will increase
asish_1069: obviously the particle will move towards net decreasing PE because it has tendency to attain least energy hence more stability hence the issue
10:1
asish_1069: y?
Anirudh_872: u must atleast agree with that
asish_1069: in the example ive given KE decreases naa?
asish_1069: although it increases after a time when its speed becomes zero. but it decreases till the speed becomes zero
10:2
Anirudh_872: so what is verdict??
Anirudh_872: *the verdict
10:4
asish_1069: the verdict is that question shud have been framed better
asish_1069: to have no confusion.
asish_1069: or the options shud be changed
Anirudh_872: :)
10:4
Anirudh_872: yes
11One more thing, in your example u have already given ur particle an initial velocity
but in the question,
havin +ve chrge is releasd frm rest
106oooooooppss... sry guys i din read the Q properly.. Yes then obviously KE WILL increase
11that happens...........don't worry
now everyone knows a little more about kinetic and potential energies than before [3]