Answer:
A. Atoms randomly crashing into each other
E. The force of one object pushing against the force of another object.
Explanation:
Forces can be classified into two categories based upon the the mode of transfer or application:
1. Contact forces
2. Non-contact forces
Contact forces are the ones which require the physical contact of the matter to get transferred and tend to create the affect. Whereas non-contact forces have the field property which transfers the affect of force from one point to another without any physical contact of the matter or the medium.
- Atoms crashing onto each other have some mass and velocity which upon collision impacts the other atoms exerts a contact force.
- The interaction between the charged particles due to their charges is always due to the electric field be it electron or proton, be it within an atom or out of an atom.
- The force between any two objects pushing or pulling each other is also possible only due to contact.
Volume = 3 cm × 3cm × 3cm
= 27 cm ³
Mass = 213 g
Density =
= <span>
</span>
<span> = 7.89 g / cm³
Thus answer is D.</span>
Answer:
200g
Explanation:
Step 1:
The balanced equation for the reaction.
2Na + 2H2O —> 2NaOH + H2
Step 2:
Determination of the number of mole of NaOH produced by the reaction. This is illustrated below:
From the balanced equation above,
2 moles of H2O produced 2 moles of NaOH.
Therefore, 5 moles of H2O will also produce 5 moles of NaOH.
Step 3:
Conversion of 5 moles of NaOH to grams. This is illustrated below:
Number of mole of NaOH = 5 moles
Molar Mass of NaOH = 23 + 1 + 16 = 40g/mol
Mass of NaOH =?
Mass = number of mole x molar Mass
Mass of NaOH = 5 x 40
Mass of NaOH = 200g
The screen will not be useful in separating the mixture of saw dust, salt and pebbles.
Answer: Option C
<u>Explanation:
</u>
The separation of individual elements from the mixture can be done easily if the size of the elements in the mixture is varying significantly. Just like in the present case, the size of sawdust and salt is very small compared to that of pebbles.
So by using sieves having pores of smaller sizes, pebbles can be separated from the mixture as pebbles will not pass through the minute pores. Even depending upon the size of pores, the saw dust can also be separated using it.
Similarly, we can use water also to separate this mixture as sawdust have least density it will float in water surface and pebbles being the highest density will sink and settle in the bottom of the container.
Remaining salt will get dissolved in water which can be obtained by heating the water in order to precipitate the salt. Even filter paper with different mess size will also help in separating this mixture. But as this mixture is not permeable through screen, the screen cannot be used to separate this mixture.
