Lower Secondary Science

[Mary Joy]

Can someone help me with this physics question.... :thankyou:


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[Mary Joy]

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Please help me with this question...Thanks

[dioprem]

Mary Joy:

Can someone help me with this physics question.... :thankyou:


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Not too much information given here, so I'm going to make the assumption that the M113 has to be afloat in pure water. In order for a body to float in a liquid, it needs to have a lower density as compared to the liquid. In the case of pure water, its density is 1000 kg/m3.

Since density = mass / volume,

1000 = 1.115 X 10^4 / volume

Hence volume = 11.15 m3

So the M113 would need a volume greater than that to stay afloat.

Hope this helps!

P.S The print is a little small so the value I used for the mass of the M113 could be wrong, but the principle is still the same.

[Dr.033430Daniel]

Mary Joy:

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http://i57.tinypic.com/i3xvo7.jpg\">

Please help me with this question...Thanks

According to the graph, when the light intensity is zero then the number of oxygen bubbles is zero. Since oxygen is a byproduct of photosynthesis, this shows that light is essential for photosynthesis to occur.

What is not 100% clear from the question is whether there was actually a data point taken with 0 light intensity. It seems so since both graphs are extended down to 0 light intensity. To cover any uncertainty in this, you could add.....

The entire apparatus could be covered to ensure zero light intensity and then the volume of oxygen collected could be measured before and after to confirm that no oxygen is produced in the dark.

[Techmummy]

Can anyone help me with q 27

Thanks in Advance

[S_Mummy]

Please help. Why is b. incorrect.


Which of the following substances is made up of four elements?
a.\t C5H7COOC2H5
b.\tNH4NO3
c.\tK2Cr2O7
d.\tNaHCO3

[Dr.033430Daniel]

Wimpy Kid:

Please help. Why is b. incorrect.


Which of the following substances is made up of four elements?
a.\t C5H7COOC2H5
b.\tNH4NO3
c.\tK2Cr2O7
d.\tNaHCO3

For choice b There is Nitrogen, 4 Hydrogens, then Nitrogen again, then 3 Oxygens. Since Nitrogen is repeated it only counts as one element.

By the way an element symbol always has either one capital letter or a capital and a lower case letter. So an element will never have two capital letters in it's symbol. Sometimes chemists do write chemical formulas where an element is repeated more than once.

Choice d has Sodium, Hydrogen, Carbon and Oxygen - 4 elements.

[S_Mummy]

Hi Dr Daniel & 45has,

Thank you very much for your reply. Ds clearly understands now.

:thankyou:

[anneshirleygilbert]

How do you balance this equation, please.


__Cu + __ HNO3 == __ CU (NO3)2 + __ NO2 + __ H2O

I’ve tried several times but can’t get it.

TIA

[Sysy]

Explain why the walls of atria are thinner than that of the walls of ventricles

Can pls help to explain the qn ?