Physics: Post your doubts here!

[Dashexdan]

Dashexdan
bro u know how to do it ?

haha no man sorry

 

[Suchal Riaz]

Can anyone tell me redspot has past papers of which board.
These questions in redspot are not CIE A level past paper questions. I can't find any.

 

[daredevil]

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s08_qp_4.pdf

Can someone pleasseee solve
Question 1b) why is frictional force = centripetal force//?? (according to marking scheme)
Question 4 bii) I did not understand why Va+Vb = 0 from the marking scheme.
question 4 c) ??!!??!
Question 5
Question 7b ii

Plzzz someone explain these questions to me!!
Physiccss!! x_X

 

[hino]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf

see question 1 b please!!
in thhe marking scheme it says that frictional force = centripetal force
how ?? i dont get it??

frictional force=centripetal force since friction provides the centripetal force
For example suppose that a driver of a car makes a sharp turn to the left of a road or u can say a turn about at constant speed. During the turn, the car travels in a circular-type path. That is, the car sweeps out one-quarter of a circle. The friction force acting upon the turned wheels of the car causes an unbalanced force upon the car and a subsequent acceleration. The unbalanced force and the acceleration are both directed towards the center of the circle thus making the car adopt a circular path.So as u can see its the friction thats causing the car to move in circular path meaning its providing the centripetal force.IF IT werent for friction the car wouldnt have been able to make a turn and would have gone straight.
SSupposeuppose

 

[daredevil]

frictional force=centripetal force since friction provides the centripetal force
For example suppose that a driver of a car makes a sharp turn to the left of a road or u can say a turn about at constant speed. During the turn, the car travels in a circular-type path. That is, the car sweeps out one-quarter of a circle. The friction force acting upon the turned wheels of the car causes an unbalanced force upon the car and a subsequent acceleration. The unbalanced force and the acceleration are both directed towards the center of the circle thus making the car adopt a circular path.So as u can see its the friction thats causing the car to move in circular path meaning its providing the centripetal force.IF IT werent for friction the car wouldnt have been able to make a turn and would have gone straight.
SSupposeuppose

ooohhh okaaayy thankkss alot!! (Y)
plzzz c if u can clear the other querries as well!!

 

[Suchal Riaz]

Please help me. I have attached question, answer and examiners comment for your ease.


Answer is A.
Examiner report says "Even many good candidates tried using 90% of atmospheric pressure and had the answer B. This illustrates the problem with algebraic answers. Perhaps if they had realised that their answer was giving a straw of length 9 metres they might have re-checked their answer."
s03qp1q20

 

[snowbrood]

Please help me. I have attached question, answer and examiners comment for your ease.

View attachment 33317
Answer is A.
Examiner report says "Even many good candidates tried using 90% of atmospheric pressure and had the answer B. This illustrates the problem with algebraic answers. Perhaps if they had realised that their answer was giving a straw of length 9 metres they might have re-checked their answer."
s03qp1q20

ok so the forces must be acting in equilibrium
upward forces= downward forces
f=P*A P is the atmospheric pressure
atmosphere is pushing the liquid upwards the weight of the liquid and reduced pressure is acting downwards
P*A=(0.9*P*A)+mg
mg=0.1P*A
mass of liquid is density*volume=p" *A*L where p" is density of liquid
p"ALg=0.1*P*A
cancel As on both sides
(P'')*L*g=0.1P
L=0.1P/(p"*g)

 

[Suchal Riaz]

ok so the forces must be acting in equilibrium
upward forces= downward forces
f=P*A P is the atmospheric pressure
atmosphere is pushing the liquid upwards the weight of the liquid and reduced pressure is acting downwards
P*A=(0.9*P*A)+mg
mg=0.1P*A
mass of liquid is density*volume=p" *A*L where p" is density of liquid
p"ALg=0.1*P*A
cancel As on both sides
(P'')*L*g=0.1P
L=0.1P/(p"*g)

Ok i got everything. But can please explain the assumption that system is in equilibrium and upward force = download force. When the kid is pushing the water upwards the upward force must be bigger.
I think thats because we are asked to find maximum height?

 

[snowbrood]

Ok i got everything. But can please explain the assumption that system is in equilibrium and upward force = download force. When the kid is pushing the water upwards the upward force must be bigger.
I think thats because we are asked to find maximum height?

well this is in equilibrium actually what that f kid can do is just suck some air from it.the rest is air pressure. so we might think that we are drawing that liquid but no that is air pressure that is doing this



but u know what without air pressure he cant(nobody can) draw any liquid from the straw. u can do it for yourself take a jar fill half of it with liquid poke the hole at the top make sure that is air tight then try to suck some liquid u will suck some after that u wont be able to draw any liquid from straw

 

[snowbrood]

Ok i got everything. But can please explain the assumption that system is in equilibrium and upward force = download force. When the kid is pushing the water upwards the upward force must be bigger.
I think thats because we are asked to find maximum height?

oh man physics is beautiful isnt it?

 

[Suchal Riaz]

oh man physics is beautiful isnt it?

mechanics is boring. relativity is astounding. quantum mechanics is weird. string theory is mind-blowing. but the relation between them, what we call physics, is beautiful.

 

[Suchal Riaz]

oh man physics is beautiful isnt it?

mechanics is boring. relativity is astounding. quantum mechanics is weird. string theory is mind-blowing. but the relation between them, what we call physics, is beautiful.

 

[daredevil]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s08_qp_4.pdf

Can someone pleasseee solve
Question 1b) why is frictional force = centripetal force//?? (according to marking scheme)
Question 4 bii) I did not understand why Va+Vb = 0 from the marking scheme.
Question 5
Question 7b ii

Plzzz someone explain these questions to me!!
Physiccss!! x_X

explaain ker do plzzz ASTAR syed1995 MustafaMotani

 

[amaz arif]

Do we have ecf in physics paper 3? I need answer quickly? Today I had a practical in my school. When measuring time, i wrote 0.0065s instead of 0.65s. I know marks will be deducted for this answer but will i get marks in the other parts which included this answer?

 

[daredevil]

yh i think we do have ecf for p3 .....
don't we??

 

[syed1995]

Do we have ecf in physics paper 3? I need answer quickly? Today I had a practical in my school. When measuring time, i wrote 0.0065s instead of 0.65s. I know marks will be deducted for this answer but will i get marks in the other parts which included this answer?

If it was School Practical.. depends on the teacher. But yes we do have ecf in CIE Practicals.. If you made that mistake in CIE you'd lose 2 marks maximum.

 

[arsalaan]

How to solve question 2 part(e) in the following paper: http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_s08_qp_5.pdf

 

[TheStallion-Reborn]

Can someone please help me grasp the required concepts of projectile motion in AS?

 

[TheStallion-Reborn]

Can someone please help me grasp the required concepts of projectile motion in AS?

a set of notes might help :-/

 

[IGCSE O/L student]

a set of notes might help :-/

Watch the tutorials in this site: http://aplusphysics.com/courses/regents/videos/vid_index.html
N.B. there might be music at the beginning of the tutorials and at the end too, so please turn down the volume at those points

 

[Suchal Riaz]

a set of notes might help :-/

there is no reference of 'projectile' motion in physics syllabus. although you are required to understand that in such motions the velocity in one direction is constant but in perpendicular direction it is accelerated. as well as basic things such as at highest point the vertical velocity will be zero etc. thats it. old questions cover details of this chapter which is not required by current syllabus.