Physics: Post your doubts here!

[Varuna0911]

hello could you help me with no 1...thanks

 

[autumnsakura]

hello could you help me with no 1...thanks

1(a) Distance is scalar, it only has magnitude, no direction. Displacement is a vector, it has magnitude and direction.

(b) Check your books it's about inertia.
(c) I don't know if you can answer like this... Since velocity is constant, acceleration is zero. As acceleration is zero, resultant force is zero. Tanker in equilibrium when there's no resultant force on it.
Resultant force balanced out by drag force on water?

 

[Varuna0911]

1(a) Distance is scalar, it only has magnitude, no direction. Displacement is a vector, it has magnitude and direction.

(b) Check your books it's about inertia.
(c) I don't know if you can answer like this... Since velocity is constant, acceleration is zero. As acceleration is zero, resultant force is zero. Tanker in equilibrium when there's no resultant force on it.
Resultant force balanced out by drag force on water?

thanks I needed to know about the vector diagram and the calculation part after that

 

[InnocentAngel]

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

 

[autumnsakura]

thanks I needed to know about the vector diagram and the calculation part after that

To draw the vector diagram, u need to use a scale. As in you measure the given line of R and find 1cm= how many newtons. Then you draw the other two lines according to the scale. Even if the two lines intially don't reach, just keep changing the angle of the lines until they meet at one point WITHOUT changing it's length. That's what I would do

 

[umarashraf]

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
Thanks in advance

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...???

 

[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