fishslayer

Ok thank you for your help (i kind have knew i couldnt be right )

I got this question sent to me:

An 2 kg mass object is held by a spring balance in a liquid of density 1200kg/m3. What reading does the spring balance show (in N)?

So i wanted to cheak my that i was doing it properly can somebody cheak what i did and say. This is what i did.

Weight = mg

Weight = 2*10

Weight = 20

Upthrust = Density of liquid/ Density of Solid (mg)

So: Density of solid = Density of liquid (mg)

Denity of solid = 1200*20

Density of Solid = 24000

Apparent wieght = mg (1- density of liquid/density of solid)

= 20 (1- 1200/24000)

= 20 (1- 0.05)

= 20*0.95

= 19N

Is that right?

Yeah as i D was right. It seems simple now. As f and E are connected (E=hf) you can narrow choices down. It cant be A or B as they dont make sense. In C in order for it to be a higher f it must have gained energy from something. There is nothnig for it to gain energy from so its D.

ok, so i have relooked over the question, done some calcualtions etc and still havent got that far. i personally dont think i have learnt enough of physics to understand some of it but could somebody please tell me what is the right answer and why it is. (i have tried to use the equations on the doppler effect etc and havent had much sucsess)

Merged post follows:

oh lol managed to answer is it

you can elimanate (sp?) A and B beacuse of the doppler shift effect and beacuse E=hf energy is proportional to frequency so it must be d.

all the information i gave in the question i wrote out is all i have to answer it.

actually personally i would jsut like the answer and the proof, ive spent at least a week on it and im getting nowhere. Everybody ive gone to for help doesnt seem to know the answer .

Why i think its C. I worked out it had to be D or C and due to sum weird thinking i came up with C.

ok but does anybody have an answer for this exact question?

RyanJ - i dont think that will help as it doesnt have values (and if you put values in i think it screws up)

ydoaPs - yeah i wasnt sure where to put it so i put it here

mm not sure about the bee one but what about this one

I turn polar bears white

and I will make you cry.

I make guys have to pee

and girls comb their hair.

I make celebrities look stupid

and normal people look like celebrities.

I turn pancakes brown

and make your champagne bubble.

If you squeeze me, I'll pop.

If you look at me, you'll pop.

95% of Harvard students cannot figure this out while almost all kindergartners get it right in less than 6 minutes.

Can you guess the riddle?

(firstly not sure if this goes here but if it doesnt then please move it)

I was set this question by somebody and i have not been able to answer it. I have a rough idea what the answer is but ive not a clue how i can prove it. Does anybody have any help?

Here is the question:

A person stands on the sidwalk when he/she hears the siren of an ambulance which approaches with velocity V. The ambulance passes in front of him/her and continues its way, getting further and further with the same velocity V. Let f1 and f2 be the frquencies of the siren heard by this person when the ambulance is approaching and when the ambulance is getting further respectively. If f0 is the frequency of the siren as heard by the ambulance driver, which statement below is true?

A - f1 < f2 and f0 is slightly larger than (f1+f2)/2

B - f1 < f2 and f0 is slightly smaller than (f1+f2)/2

C - f1 > f2 and f0 is slightly larger than (f1+f2)/2

D - f1 > f2 and f0 is slightly smaller than (f1+f2)/2

P.S. I narrowed it down myslef to C or D and i am confident it's C but i do not know if thats true or how to prove im right/wrong.