Physics: Post your doubts here!

[princess Anu]

Someone help
Ans is 1.5
Why is my ans coming wrong

 

[Aishayasin]

Can Anyone Help me with

Answer is B how?

 

[Aishayasin]

A ball is thrown vertically downwards at 4.0 m/s from a height of 120 cm .With which speed does it hit the ground? Ignore air resistance.
A 4.8 m/s B 6.3 m/s C 40 m/s D 49 m/s
Answer is B

 

[Aishayasin]

Someone help
Ans is 1.5
Why is my ans coming wrongView attachment 60535

If it takes 12 hours to go from low tide to high tide and back to low tide, that means it takes 12 hours to go from 1.0m, to 3.0m and back to 1.0m.

So in half of 12 hours= 6 hours it goes from 1 to 3
And in half of that= 3 hours it goes from 1 to 1.5.

Try drawing a wave starting from the lowest point (1.0m) going to the highest point (3.0m) and coming back to the lowest point (1.0m).
Draw a line through where it is 1.5m, which is half way between 1m and 3m. If the whole wave is 12 hours you will see that at a quarter of twelve hours the wave crosses the line you drew for 1.5m

 

[ahmedish]

if we get 14.6 on analogue, when we sample it, do we round up or down?
my teacher says down
my book says nearest number
think i solved an exam where it was nearest number and not down

 

[farhan141]

14.6 is near to 15 so 15.

 

[farhan141]

if we get 14.6 on analogue, when we sample it, do we round up or down?
my teacher says down
my book says nearest number
think i solved an exam where it was nearest number and not down

 

[ahmedish]

lol my teacher is so bad

 

[farhan141]

lol my teacher is so bad

Happens

 

[ahmedish]

Happens

which p4 did u take

 

[farhan141]

42

 

[i_try9621]

Anyone help me with this question? Ans for this is B.

 

[i_try9621]

see solution 64 at
http://physics-ref.blogspot.com/2014/11/physics-9702-doubts-help-page-12.html

I did, but what I don't get it is, as quoted from the blog "Since the mass of the water is spread all over the volume it occupies, the centre of mass should be considered when calculating the (gravitational) potential energy." Why do they consider the centre of mass ? Do we generally consider the centre of mass while considering the Potential energy of an object?

 

[i_try9621]

we always consider the centre of mass. else we would have to calculate the potential eenrgy of each molecule since their positions (height) are each different

Ah! Thanks!

 

[Bhaijan]

9702_s09_qp 1
Ans is C
im confused there are two types of beta decay
someone please explain the answer
Q

 

[Saad the Paki]

9702_s09_qp 1
Ans is C
im confused there are two types of beta decay
someone please explain the answer
QView attachment 60625

In the old syllabuses, there was only one type of Beta decay,which is B- decay . So whenever they mention beta decay we will assume it to be B- .

So in B- neutron decays to proton increasing the proton number while keeping nucleon number the same. But this question is backwards. So it must have one less proton to form this Calcium nuclide. So ans should be C

 

[Bhaijan]

The question is from 9702_s09_qp_1 and the answer is B.
In my opinion the answer should have been C because if we were to consider the water on both the tanks and their heights, the total PE would come out to be mgh/2. If we were to subtract this from the original height, the loss would come out to be mgh/2. [All this is done if we were to assume that the new height of the water in each tank would be 1/2h]

 

[Umair Abid]

Yeah so I made a huge blunder in my Physics paper 3 practical exam. Instead of measuring and recording length of x in question 1, I measured it from the opposite side so my readings are kind of 1-x rather than x. This did mess up my trend in graph as well.

Up to how many marks will I lose for the table and the graph because of this?

(Since no one replies in threads, I'll post this here xD)

 

[Hania Ahmer]

What r factors affecting drift velocity?

 

[Hania Ahmer]

Two copper wires connected in parallel, one wire is thick n other is thin, why is drift velocity same in both? (According to pacific phy) ..oh and assuming a constant temperature...