Edexcel PHYSICS Doubts

[Ibiza279]

i need the ryt answer wid explanation for this question
5.   Two points on a progressive wave differ in phase by   radian. The distance between them is 0.50 m. The frequency of the oscillations is 10 Hz. The maximum speed of the wave is
A   2.50 m s–1
B   5.00 m s–1
C   12.5 m s–1
D   40.0 m s–1

By the way the way, how do u solve this question after knowing that the value for radian is pi/4 lol

[GodOfWar]

By the way the way, how do u solve this question after knowing that the value for radian is pi/4 lol

Well
wavelength is 2 pi(360^o).
So wavelength of this wave = 8 x0.5 = 4m
V=f*wavelength which is 10 x4 = 40 m/s

[Ibiza279]

aaah Thanks dude, now i get it

[GodOfWar]

no prob

[7ooD]

ok this thing is giving me a headache im afraid it comes tommorow and i dnt get it i understand that the spectra thingy is the process in which we have a paper and when light is shined like from the sun we get lines of wavelengths corresponding to the elements from which the light is made of and elements emit light so each element is resposible for different colours of light but wat i dnt get is how these elements emit lite from the sun??? and i kno that if an element example hydrogen absorb light it uses it to get excited and we saw a dark line in the spectra but how does it absorb that lite??? wat lite exactly does it absorb!!! when it emits lite

last thing is a question from exam wizard the one t.q gave us it says

one way to study the energy levels of an atom is to scatter elecrons from it and measure their kinetic energies before and after the collision. if an electron of k.e 0.92 ev is scattered from a lithium atom which is initially in the -5.02 ev level the scattered elecron can have only two possible k.e s
 state these two k.e values and explain what has happened to the lithium atom in each case ( u should assum that the lithium atom was at rest both before and after the collision) -5.02 is the ground level in the diagram

[7ooD]

plz someone clear my crazy doubt i no i posted it very late but i waz so buzy if i become a mod like in 20 yrs i will give him/her free bans :p it will b appreciated if answered

[Fenomenoe9]

i have no freaking idea m8

[Fenomenoe9]

Actually nm i think i know for the second question the past paper one.:

The first kinetic energy 1 is 0.92 V ... now the explanation is that nothing happens to the atom it stays at -5.02 (eV) level and nothing happens to it.

The second kinetic energy is i dont know sorry but im trying to think about it.

Hope it helped a bit

[7ooD]

ye thx but why does it stay nd nothing happens

[S.M.A.T]

Please i need help in a question.
#A ceiling fan is turning at a rate of 100 revolutions per minute.A spider is clinging to a blade of the fan.If the spider experiences a centripetal acceleration greater than 0.3g,it will lose its grip on the blade and be flung off. how far from the centre of the fan can the spider safely go?
Please give the complete solution.
The answer in the book is 1.05m

(g means acceleration due to gravity)

[Saladin]

Please i need help in a question.
#A ceiling fan is turning at a rate of 100 revolutions per minute.A spider is clinging to a blade of the fan.If the spider experiences a centripetal acceleration greater than 0.3g,it will lose its grip on the blade and be flung off. how far from the centre of the fan can the spider safely go?
Please give the complete solution.
The answer in the book is 1.05m

(g means acceleration due to gravity)

Is this AS or A2?

If it is A2, I am afraid I can not answer the question....yet...

[S.M.A.T]

this is A2

[Saladin]

Sorry then 

[Saladin]

Alrite guys, I need a little help in these questions. I have finished them, I just want to check, because I do not have the mark-schemes to the questions.

I have attatched the questions in a .pdf.

For 1(b): Do we add both the weights of the cart and the human? I did so, and I got an answer of 4750 Kgms^-1

2(a): I wrote that the ball does work against air resistance, and thus, it reduces the speed of the ball and therefore the momentum.
2(b): I said, that the wind might be against the batsman, and thus this may increase the ball's momentum. And this will require more energy to work against.

4(a): Is the answer 1025 Kgms^-1?
4(b): Some of the momentum is absorbed by the dash-board? I am not to sure about what the question is asking.

5(b): I got 5.736 Kgms^-1
5(c): I got 478 N
5(e): The rubber will bounce back with more speed, meaning that it had a greater impulse. Thus this means, that the force will be greater, and thus more advantageous.

Please can anyone help me check my answers?

[astarmathsandphysics]

here are my answers