Physics: Post your doubts here!

[Mustehssun Iqbal]

yeah man thanx gud explanation. another question when an electron is travelling in a uniform electric field and it goes towards the positive plate, will it accelerate or move by constant velocity????? i think its constant velocity because a constant force is being applied on it because of the uniform electrical field. PLease answer

good question. no it will accelerate.
F= ma, Newton's second law, an object "accelerates" in the direction of the applied force. Here, electric force is applied so the particle will accelerate. Whenever force is applied, the object accelerates. Coming back to your question, when the force is constant, constant acceleration will be there.
Force is directly proportional to acceleration. When there's no force, then there's no acceleration. But when there's constant force, there's constant acceleration. Hope that helps...

 

[raamish]

good question. no it will accelerate.
F= ma, Newton's second law, an object "accelerates" in the direction of the applied force. Here, electric force is applied so the particle will accelerate. Whenever force is applied, the object accelerates. Coming back to your question, when the force is constant, constant acceleration will be there.
Force is directly proportional to acceleration. When there's no force, then there's no acceleration. But when there's constant force, there's constant acceleration. Hope that helps...

well its a uniform electric field so shouldnt force be constant ?

 

[Mustehssun Iqbal]

well its a uniform electric field so shouldnt force be constant ?

yes force is constant. but constant force always produces constant acceleration.
According to Newton's second law, F= ma, we can see that force and acceleration are directly proportional to each other. So when force increases uniformly, acceleration increases uniformly. And uniform acceleration means, uniform change in velocity. Hence velocity is not constant.

 

[InnocentAngel]

Hey friends please help me with this P3 question.
October/November 2005
(ii)
Estimate the number of oscillations that would need to be timed in order to make

the percentage uncertainty in T equal to 1%. Show your working.

Thanks in advance.

 

[Albert Einstein]

All what u have to do is 0.3/t=0.01
Find t=30 s
so give and estimate of number of oscillations in 30 s....
simple

 

[Varuna0911]

hello could you help me out on mcq questions of June 2012 p12 Q4, 13, 15, 17, 18, 19, 24, 25

 

[Albert Einstein]

hello could you help me out on mcq questions of June 2012 p12 Q4, 13, 15, 17, 18, 19, 24, 25

Quest 4

diameter of metal rod = (3.5 + (31 x .01)) = 3.85

since cross sectional area is given by A=(pie d^2)4

area = 11.4
Ans B

....too much quest...dr

 

[Varuna0911]

its okay, thank you very much...you may do one question per day or week i would appreciate it

 

[raamish]

yes force is constant. but constant force always produces constant acceleration.
According to Newton's second law, F= ma, we can see that force and acceleration are directly proportional to each other. So when force increases uniformly, acceleration increases uniformly. And uniform acceleration means, uniform change in velocity. Hence velocity is not constant.

great got it thnx

 

[Mustehssun Iqbal]

great got it thnx

rethink it for yourself in order to remember it strongly...

 

[bamteck]

Mustehssun Iqbal or Albert Einstein or someone else Please help me for this question.
Please help me for June 2004 p2 no. 3 (b)(ii) also. I have trouble in answering.
Thank you very much in anticipation.

 

[Haseefa]

Could someone help me with this?

If a raindrop were to fall from a height of 1 km, with what velocity would it hit the ground if there was no air resistance?

 

[badrobot14]

Could someone help me with this?

If a raindrop were to fall from a height of 1 km, with what velocity would it hit the ground if there was no air resistance?

try this: no resistance means const acceleration...

use s = ut +0.5at^2
s = 0t + 0.5*9.8*t^2
as s=1000 get t.

use
v = u + at = 0 + 9.8*t
put t from prev step and get v...

do u get the right answer...? (this is a maths qustn n I like maths!)

 

[badrobot14]

Mustehssun Iqbal or Albert Einstein or someone else Please help me for this question.
Please help me for June 2004 p2 no. 3 (b)(ii) also. I have trouble in answering.
Thank you very much in anticipation.View attachment 14708

use paralellogram method of vector addition of forces to add the forces in that diagram:

http://www.tutorvista.com/physics/parallelogram-law-of-forces

at 11 min 20 sec in this vid this guy teaches that:

 

[bamteck]

Please help me for June 2004 p2 no. 3 (b)(ii)
Thanks.

 

[Mustehssun Iqbal]

great got it thnx

you're welcome!

 

[bamteck]

you're welcome!

Please help me for June 2004 p2 no. 3 (b)(ii)
Thanks.

 

[Varuna0911]

could you help me with June 2012 P12 Q13?

 

[Haseefa]

try this: no resistance means const acceleration...

use s = ut +0.5at^2
s = 0t + 0.5*9.8*t^2
as s=1000 get t.

use
v = u + at = 0 + 9.8*t
put t from prev step and get v...

do u get the right answer...? (this is a maths qustn n I like maths!)

Yes, I got it, JazakAllah Khair. ohh n this was a physics question...

Another quest, if there is no air resistance, what does it tell about the speed?

 

[badrobot14]

Yes, I got it, JazakAllah Khair. ohh n this was a physics question...

Another quest, if there is no air resistance, what does it tell about the speed?

wa iyyakum..
no air resistance means nothing stopping it from comming down so constant acceleration.. that tells us speed keeps increasing at a fixed rate (Acceleration of 9.8) until SPLAT it hits the ground.... with air resistance the speed increases till a fixed value and until that time air resistance force also increases until the upward and downward forces are equal and your drop comes down with a constant velocity.. we call that const velocit Terminal Velocity if my memory servers me right...