Physics: Post your doubts here!

[j4minghou]

does anyone know how to solve Q36,37?
9702/11/M/J11 Paper 1
*much thanks if you can provide a more detail explanation, cuz i am lil weak in electric circuit XP

 

[j4minghou]

9702/11M/J11 paper1 2011
Q32 A battery is marked 9.0V. What does this mean?

A. each coulomb of charge from the battery supplies 9.0J of electrical energy to the whole circuit.
B. the battery supplies 9.0J to an external circuit for each coulomb of charge
C. The potential difference across any component connected to the battery will be 9V
D. there will be always 9.0V across the battery terminals

*my ans is B. by the definition of (e.m.f of 12V- 12J of electrical energy is supplied to drive one coulomb of charge round a complete circuit) option A seems correct but doesnt make sense so ans should be B right?

same paper for Q31

A copper wire of cross-sectional area 2.0mm^2 carries a current of 10A. How many electrons pass through a given cross-section of the wire in one sec?
my ans is C. 6.3x10^19 (we just have to ignore the area thingy right?)

 

[Albert Einstein]

9702/11M/J11 paper1 2011
Q32 A battery is marked 9.0V. What does this mean?

A. each coulomb of charge from the battery supplies 9.0J of electrical energy to the whole circuit.
B. the battery supplies 9.0J to an external circuit for each coulomb of charge
C. The potential difference across any component connected to the battery will be 9V
D. there will be always 9.0V across the battery terminals

*my ans is B. by the definition of (e.m.f of 12V- 12J of electrical energy is supplied to drive one coulomb of charge round a complete circuit) option A seems correct but doesnt make sense so ans should be B right?

same paper for Q31

A copper wire of cross-sectional area 2.0mm^2 carries a current of 10A. How many electrons pass through a given cross-section of the wire in one sec?
my ans is C. 6.3x10^19 (we just have to ignore the area thingy right?)

For Q32
option A is right..ur definition abt emf is also right ..bt z option u selected is wrng i wuld rather ask u to start by elimination(one of the best way to deals with MCQ)
Let start distinguish between A and B
B states that the battery supplies energy to the external circuit..which is wrng it supplies also to internal circuit as a battery do have an internal resistance( u should knw z difference between internal and external circuit) hence zis ans is eliminated and A is the correct ans.
Concerning A-from defn of emf..energy supplied to drive 1 C of charge round a complete circuit(whole circuit) means zat z charge will carry and supply the energy as there is not any medium for zis task....hence the statement each coulomb of charge supply 9J of work is correct...it make sense...

 

[Albert Einstein]

n 4 31 we have to ignore the area..

 

[Anish Niroula]

Where can we find the past paper of may june 2012 and its marks scheme..plz help me

 

[Bhavesh Salvatore]

The maximum safe speed of a car rounding an unbanked corner is 20 m/s when the road is dry. The maximum frictional force between the road surface and the wheels of the car is halved when the road is wet. What is the maximum safe speed of the car to round the corner when the road is wet ?

 

[Mustehssun Iqbal]

The maximum safe speed of a car rounding an unbanked corner is 20 m/s when the road is dry. The maximum frictional force between the road surface and the wheels of the car is halved when the road is wet. What is the maximum safe speed of the car to round the corner when the road is wet ?

 

[Bhavesh Salvatore]

Thankx

 

[Mustehssun Iqbal]

Thankx

you're welcome
and check the answer...

 

[smzimran]

Mashallah! Mustehssun Iqbal
Nice !

 

[Mustehssun Iqbal]

Mashallah! Mustehssun Iqbal
Nice !

thanks!

 

[raamish]

if a steel ball is falling in air will it always hit the ground at constant acceleration or will its acc. be affected by several bounces??

 

[Mustehssun Iqbal]

if a steel ball is falling in air will it always hit the ground at constant acceleration or will its acc. be affected by several bounces??

no acceleration remains constant, towards the ground. acceleration doesn't get affected by several bounces. It's always downwards towards the ground. Acceleration is caused by gravitational force. It's an effect of the gravitational force which is downwards. F= ma, Newton's second law, an object accelerates in the direction of the applied force.
Yes while bouncing, at points where the ball is in contact with the ground, at that point only, acceleration differs considerably because there are two forces acting vertically now, gravitational force and normal contact force, so the acceleration at that point will be the effect of the resultant of the two forces. That's deep. Other than the point of contacts, acceleration is always towards the ground.
Hope you got it.

 

[raamish]

no acceleration remains constant, towards the ground. acceleration doesn't get affected by several bounces. It's always downwards towards the ground. Acceleration is caused by gravitational force. It's an effect of the gravitational force which is downwards. F= ma, Newton's second law, an object accelerates in the direction of the applied force.
Yes while bouncing, at points where the ball is in contact with the ground, at that point only, acceleration differs considerably because there are two forces acting vertically now, gravitational force and normal contact force, so the acceleration at that point will be the effect of the resultant of the two forces. That's deep. Other than the point of contacts, acceleration is always towards the ground.
Hope you got it.

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

 

[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