Physics Paper 2

[Zeuss]

Yeah i thought that too...

The initial and final speed act in opposite directions...
So one value becomes positive and the other negative.

I got 47 m/s for change in velocity as well...

Since acceleration is CHANGE IN VELOCITY per unit time...

But the value i got is quite large so i wonder...

Anyone got an idea???

I used -47m/s to find the acceleration
a = ( - 47)/ 0.0013
I got a big number as well( in fact its a very small number since its negative). But it make sense, the ball DECELERATES so much that it goes from 25 to - 22 in such a small amount of time. I just worried whether i wrote the unit for the acceleration. And i left the answer as 3 sig fig. (xxx00). Is that alrite?. And i used that value to find the force.

 

[bamteck]

Then how to achieve a distinction "1 or 2" in physicx?

U think paper 1 & 4 gonna work?

 

[bamteck]

U think paper 1 & 4 gonna work to cover the paper 2 to achieve a distinction ?

 

[Prince III]

Then how to achieve a distinction "1 or 2" in physicx?

U think paper 1 & 4 gonna work?

if you want a distinction then your entire paper 1 , paper2 , and paper 4 should be 100 % correct
means 145 / 145 can only make up to a distinction

 

[bamteck]

I mean a distinction "2" or a good credit "3" ?

The paper 1 & 4 can cover the paper 2?

 

[Pals_1010]

Yeah i left the answer to 3 sig fig as well...
For the force i used this value too

Let's pray its right!!!

 

[carolinetcw]

:? it was actually easy yet really unexpected , nothing similar like all the past years i've done before. i lost ten marks alone due to careless mistake , didn't know i didn't actually remember how to draw a transformer?! anyway , what's the resistance of the filament bulb and how the variable resistor protects it ? i think i had cancelled the initially correct answer. i reversed my answers to those two in the last minute.

does the resistance decreases?
and to vary current so as to protect the bulb?

 

[carolinetcw]

yes , acceleration and change in velocity was in negative!!!

 

[carolinetcw]

yes , acceleration and change in velocity was in negative!!!

Re: Physics Paper 2

Post by Zeuss » Sat Oct 16, 2010 2:13 pm

Pals_1010 wrote:Yeah i thought that too...

The initial and final speed act in opposite directions...
So one value becomes positive and the other negative.

I got 47 m/s for change in velocity as well...

Since acceleration is CHANGE IN VELOCITY per unit time...

But the value i got is quite large so i wonder...

Anyone got an idea???

 

[Zeuss]

:? it was actually easy yet really unexpected , nothing similar like all the past years i've done before. i lost ten marks alone due to careless mistake , didn't know i didn't actually remember how to draw a transformer?! anyway , what's the resistance of the filament bulb and how the variable resistor protects it ? i think i had cancelled the initially correct answer. i reversed my answers to those two in the last minute.

does the resistance decreases?
and to vary current so as to protect the bulb?

Yea, i was cracking my head over this one. I don't know what i answered for how the resistance change as brightness increases. And for the "how does using a variable resistor protects the filament bulb?", i said voltage across the bulb is slowly increased so the filament does get overheated. I doubt that'll be correct.

 

[Pals_1010]

Since a filament lamp is non-ohmic, i thought that as brightness increases, current (or voltage whichever) must increase. As current increases, the temperature of the filament increases and thus resistance also increases????

What do you think???

 

[Prince III]

thanks, but the rectifier was not mention in the syllabus

20. D.C. Circuits
Content
20.1 Current and potential difference in circuits
20.2 Series and parallel circuits
Learning Outcomes
Candidates should be able to:
(a) *draw circuit diagrams with power sources (cell, battery or a.c. mains), switches (closed
and open), resistors (fixed and variable), light dependent resistors, lamps, ammeters,
voltmeters, magnetising coils, bells, fuses, relays, light-emitting diodes and rectifying
diodes.
(b) state that the current at every point in a series circuit is the same, and use this in
calculations.
(c) state that the sum of the potential differences in a series circuit is equal to the potential
difference across the whole circuit and use this in calculations.

hence indirectly it was mentioned

 

[Pals_1010]

Source: GCSE Physics

"For a filament lamp, the temperature of the filament is most definitely not constant (it must to get hot in order to give out light!)

The resistance of a lamp's filament (the long, thin, coiled wire) increases dramatically as the current increases, resulting in the second graph below..

"

The second graph shows that the gradient decreases.

I/V = 1/R decreases.

So resistance increases....

 

[Zeuss]

Source: GCSE Physics

"For a filament lamp, the temperature of the filament is most definitely not constant (it must to get hot in order to give out light!)

The resistance of a lamp's filament (the long, thin, coiled wire) increases dramatically as the current increases, resulting in the second graph below..

"

The second graph shows that the gradient decreases.

I/V = 1/R decreases.

So resistance increases....

Yah, i wrote that resistance increases too. I remember my teacher always mentioning this.

 

[Zeuss]

FIREMAN QUESTION.
Is Moment M = 4200Nm?
Is Force R to cancel out Moment M = 840N?
Is the third factor~~ = Weight of the ladder?

 

[Pals_1010]

Yeah i got the moment 4200Nm.

But the force to counter the moment, i got it 350N i think?

and the third factor i put weight of ladder as well...

 

[Zeuss]

Yeah i got the moment 4200Nm.

But the force to counter the moment, i got it 350N i think?

and the third factor i put weight of ladder as well...

Hey Pals_1010, i cudn't think of any ways to find out the force R to cancel the moment. I assumed since both forces acting from the same point, the same force anticlockwise will cancel it. (I used F1D1=F2D2). How did u get 350?

 

[Prince III]

Yeah i got the moment 4200Nm.

But the force to counter the moment, i got it 350N i think?

and the third factor i put weight of ladder as well...

Hey Pals_1010, i cudn't think of any ways to find out the force R to cancel the moment. I assumed since both forces acting from the same point, the same force anticlockwise will cancel it. (I used F1D1=F2D2). How did u get 350?

clockwise moment = anticlockwise moment

4200Nm = F x 12
F = 350 N

the third factor was weight of the ladder from it's centre of gravity

 

[Zeuss]

Why use 12? Isn't it suppose to be 5 since is perpendicular distance from the pivot?

 

[Prince III]

Why use 12? Isn't it suppose to be 5 since is perpendicular distance from the pivot?

no we have to take the perpendicular distance of 12 m which was the height of the building