[SophieLisa96]

(Original post by saq96)
Doesn't the resultant force increase in the first 2 seconds because of the acceleration ?

maybe i don't know, i mucked up that question completely i didn't read it properly!
I think it was okish, the grade boundaries won't be extremely high, but not too low... hoping for 33,34, or 35 for a*?

[rileyg100]

any chance of a full mark scheme with the marks?

[saq96]

(Original post by osama2)
hey u know about the car one. question about acceleration in 2 secs.....i wrote that driving force decreases and friction increases which results in a resultant force in the frictio direction.

I don't think it will be be the friction direction because the car is accelerating in the driving force direction

[SmellyK.]

(Original post by goggly)
did anyone get 30, for the 36 volts thing and 1.2 volts thing, can't remember the question properly

yepp i got that too (:

[DeeCFC18]

In the kinetic energy question was the bike supposed to be stationary or not ? think i've got around 41/45 100 ums?

[jones2596]

Please can someone explain to me why on question 4 the current doubles? I initially wrote this then crossed it out and wrote it would stay the same as if voltage and resistance were directly proportional it wouldn't actually change current..

For instance:
Voltage = current x resistance

Let's say voltage is 6 and resistance is 3. This would make current 2 amps.

And then if it became 12 volts and 6 ohms the current would still be 2 amps.

I'm so confused....

[DeeCFC18]

(Original post by jones2596)
Please can someone explain to me why on question 4 the current doubles? I initially wrote this then crossed it out and wrote it would stay the same as if voltage and resistance were directly proportional it wouldn't actually change current..

For instance:
Voltage = current x resistance

Let's say voltage is 6 and resistance is 3. This would make current 2 amps.

And then if it became 12 volts and 6 ohms the current would still be 2 amps.

I'm so confused....

I think it is to do with direct proportion can't remember though i'm afraid

[girlwithouthands]

(Original post by Frankster)
You've contradicted yourself there. The certain amount of voltage and the level of voltage in the circuit has to be the same.

The bigger the resistance of a component the bigger its share of the supply p.d. So the supply remains the same, however the p.d. only changes in the component, and unless the q asked "of changing the voltage in each component" (which I think it didn't), the battery answer is correct.
So Variable resistor affects only the amount of current. If resistance is high, current is low.

Therefore, battery is correct answer. In the exam I wrote: "Battery. You can change the number of cells in the battery pack so you can vary the amount of p.d."

Sorry, but the variable resistor does not "only affect the amount of current".

This is the formula for calculating p.d./voltage: resistance x current.

The variable resistor causes the resistance (and, yes, the current) to change. As these numbers change, the voltage changes too. Ergo, it's the variable resistor that affects the voltage travelling through the circuit.

You can switch - or alter, but even then you wouldn't be using the same battery shown connected in the circuit - the battery, but you can't change the amount of voltage that specific battery is supplying.


That's just my opinion, though, of course.

[iBillyB]

COuld someone explain how people got 2160 joules for the energy? I forgot the equation

[k.lunstone]

(Original post by Sheel1)
It said Observation lol

lol no it didnt :P it said 'what can he conclude from his observation?' x

[k.lunstone]

(Original post by Fas)
yeah i found it really easy , but it will probably be lower i know A* was 38/45 for January 2011 Unit 2 Chemistry , but that was much easier than this one lol

Yeah although for a more accurate idea of what the grade boundaries will be it is probably best to look at past physics boundaries as chemistry has really high ones.... it wont be higher than 34 A* as that is the highest it has ever been in physics

[Muslim.]

(Original post by DeeCFC18)
In the kinetic energy question was the bike supposed to be stationary or not ? think i've got around 41/45 100 ums?

ah not bad. i think i got 45/45

[k.lunstone]

(Original post by girlwithouthands)
Sorry, but the variable resistor does not "only affect the amount of current".

This is the formula for calculating p.d./voltage: resistance x current.

The variable resistor causes the resistance (and, yes, the current) to change. As these numbers change, the voltage changes too. Ergo, it's the variable resistor that affects the voltage travelling through the circuit.

You can switch - or alter, but even then you wouldn't be using the same battery shown connected in the circuit - the battery, but you can't change the amount of voltage that specific battery is supplying.



That's just my opinion, though, of course.

i cant quite remember if it was a parrallel or series circuit...if it was a parralell one changing the battery will have no affect..but if it is a series circuit then it will x

[DeeCFC18]

(Original post by Muslim.)
ah not bad. i think i got 45/45

Thats great ! was the bike stationary coz it wasn't peddling?

[DeeCFC18]

(Original post by k.lunstone)
i cant quite remember if it was a parrallel or series circuit...if it was a parralell one changing the battery will have no affect..but if it is a series circuit then it will x

It was a series

[k.lunstone]

(Original post by Aidanb90)
The question about the skateboard slowing down,

I'm sure it said what happens to the kinetic energy?
Lost to surroundings converted to heat and sound because of friction.

. . . Anyone else read it that way? Or am I mental.

it said the skateboard slows down and loses kinetic energy, explain why it does this in terms or momentum

[k.lunstone]

(Original post by DeeCFC18)
Thats great ! was the bike stationary coz it wasn't peddling?

lol no! the whole point of the question was that it was an electric bike :P

[kman123456]

(Original post by iBillyB)
COuld someone explain how people got 2160 joules for the energy? I forgot the equation

0.5 x 120 ( the mass of the bike was 30kg and the mass of the biker was 90kg) x 36 ( 6 ms ^2)

[kman123456]

See the question about the graph of voltage and current and the question was about 'what may have coursed the anonymous results' I put a change in temperature, because ohms says that they are proportional only if the temperature is constant.

[SuparNoob]

Just to be clear, you had to state that you connected 30 1.2 V cells together to make a 36V power supply. Simply '30' as an answer won't suffice if I recall the question correctly.