Physics: Post your doubts here!

[umarashraf]

View attachment 15551

is the answer A...???

 

[guitar]

Hi everyone .. please help me out with this problem, i cannot understand the solution provided.
Q)In an experiment, a radio-controlled car takes 2.50 ± 0.05s to travel 40.0 ± 0.1m.
What is the car’s average speed and the uncertainty in this value?
(P.S :Source of the question is physics P1.may/june.2005)

 

[InnocentAngel]

2.7 x 10 ^ 25 m ^-3 ... what is this mate...??? 2.7 into 10 raise to power 25m(what is this "m") raise to power -3...???

lol
In words : 2.7 times 10 to the power of 25 . This value has as units : per cubic metre . m is metre . It means that in 1 metre cube, there is 2.7 x 10 ^25 molecules . Please help me friend .

 

[VelaneDeBeaute]

Hi everyone .. please help me out with this problem, i cannot understand the solution provided.
Q)In an experiment, a radio-controlled car takes 2.50 ± 0.05s to travel 40.0 ± 0.1m.
What is the car’s average speed and the uncertainty in this value?
(P.S :Source of the question is physics P1.may/june.2005)

The car's average speed will be the quotient you receive when you divide the certain value for distance by that of the time. You'll get 40/2.5 = 16! The uncertainity could be calculated as: (I'm using *u* to represent uncertainity in .. )
uSpeed/actual value of speed obtained = udistance/actual value of distance + utime/actual value of time

 

[snowbrood]

is the answer A...???

yes buddy can u prove how

 

[zephyr86]

Can anyone solve m/j 04 paper 2 question 1(b) and 2(b)?
Thanks.

 

[guitar]

The car's average speed will be the quotient you receive when you divide the certain value for distance by that of the time. You'll get 40/2.5 = 16! The uncertainity could be calculated as: (I'm using *u* to represent uncertainity in .. )
uSpeed/actual value of speed obtained = udistance/actual value of distance + utime/actual value of time

thank you but ive tried that and the answer comes +/- 0.36 but the correct answer(as the mark scheme shows) is +/- 0.4 .....
all i am asking is that, is the sf changed into 1(rounded off in 1 decimal place), or anything else....?

 

[Albert Einstein]

Can anyone solve m/j 04 paper 2 question 1(b) and 2(b)?
Thanks.

For next part reflect the graph in the x-axis u'll get ur answer but the amplitude should be aprroximate to 7 squares(smaller ones)

 

[Silent Hunter]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_22.pdf


asalamoalikum wanted to ask something.... can we use 2as = v^2 - u^2 ?? in the Q2 (a)(ii) ?

thanks alot and JazakAllah

anyone?

 

[VelaneDeBeaute]

thank you but ive tried that and the answer comes +/- 0.36 but the correct answer(as the mark scheme shows) is +/- 0.4 .....
all i am asking is that, is the sf changed into 1(rounded off in 1 decimal place), or anything else....?

Yeah the answer is written as 0.4 because uncertainity is always given to 1 significant figure!

 

[VelaneDeBeaute]

anyone?

I think we can! Did you try getting out the answer using this formula?

 

[umarashraf]

yes buddy can u prove how

till T/2 time, the velocity has positive sign... indicating that the displacement was done in a specific direction.... after T/2 time the velocity has changed sign but the graph has same gradient...so displacement has been made in opposite direction till T time...

 

[Hasnain Ali Mirza]

Help

A motorist travelling at 10 m/s
can bring his car to rest in a distance of 10 m.
If he had been travelling at 30 m/s
, in what distance could he bring the car to rest using the same
braking force?

I have no idea how to solve this... Plz help!

 

[autumnsakura]

Hey buddies could someone please help me with these questions ? It's from the physics Cambridge book.
Here :
Question 1 .
The number of molecules per cubic metre of air at standard temperature and pressure is about 2.7 x 10 ^ 25 m ^-3 .
What is the average separation of these molecules ?
ANSWER : 3.3 x 10 ^ -9

Question 2.
A metal box in the form of a cube of side 30 cm is filled with air at atmospheric pressure (1.01 x 10 ^5 Pa ) at 15 degrees Celsius. The box is sealed and heated in an oven to 200 degrees Celsius. Calculate the net force on each side of the box.
ANSWER : 5.8 x 10^3 N

Thanks in advance

For Q1, cube root 2.7 x 10 ^ 25 m ^-3 and you get 6.46 x 10^-9 m. Divide the answer by two again and you get the final answer. I don't know why divide by two though...
For Q2, use P1/T1 =P2/T2 to get the pressure when box is 200 degree celsius. Remember that temp should be in Kelvin. You should get 1.65 x 10^ 5 Pa. Since it says net force, find its net pressure. Outside the box there's atmospheric pressure of 1.01 x 10^5 Pa already. Inside the box, there's 1.65 x 10^5 Pa. So minus that and you get 6.5 x 10^4 Pa. That times the area which is 0.09m squared, you'll get the final answer

 

[Abhishek Neogi]

Help

A motorist travelling at 10 m/s
can bring his car to rest in a distance of 10 m.
If he had been travelling at 30 m/s
, in what distance could he bring the car to rest using the same
braking force?

I have no idea how to solve this... Plz help!

Tobi will help you solve it!
Alright
u = 10 m/s
v = 0 m/s
s = 10 m

That's the first case
So...
You gotta find the retardation of the car first [Basically negative acceleration]
So....
Yeah
* = Multiply

V*V = U*U - 2*a*s
0 = 100 - 20a
-100 = -20a
a = 100/20 =( 5m/s*s)

That's the acceleration of your car! CAR FTW ! XD

Now the question is IF he were to travel at 30m/s,what'd be the distance


Therefore use the same equation again nacho

But in this case:
u = 30 m/s
v = 0m/s
s = ??? m
a = 5 m/s*s


V*V = U*U - 2*a*s
0 = 30*30 - 2*5*s
0 = 900 - 10s
- 900 = -10s
s = -900/-10 = 90m

90m OMG. That's the answer lol xD


btw doesn't a motorist drive a motorcycle instead of a car?How can a biker drive a car at the same time when he's driving a bike?:/

 

[raamish]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s07_qp_2.pdf
how do we solve 2d and 5c. I dont have any clue. Help me out please.

 

[Yousif Mukkhtar]

http://www.xtremepapers.com/papers/...nd AS Level/Physics (9702)/9702_s10_qp_13.pdf
Can someone explain Q2.

 

[maleeha123]

hey i want the link for phys june 2012 papers........guys guide me

 

[autumnsakura]

hey i want the link for phys june 2012 papers........guys guide me

http://olevel.sourceforge.net/papers/
Look for subject code 9702

 

[autumnsakura]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_13.pdf
Can someone explain Q2.

The easiest way to do this is to substitute V with a number such as 10. So X would be 10 cos angle and Y would be 10 sin angle. Substitute in two angles, for example 30 degrees and 60 degrees. Then compare the X and Y obtained from the two different angles.