physics notes for class 10
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Answers:College PE is not difficult. The exercise and skills that you receive will be to your benefit./
Answers:buddy use book-LAKHMIR SINGH AND MANJEET KAUR,for class 9th. ans1. use v=u+at ans2. use v=u+at here v=0(brakes applied) ans3. acceleration ans4. speed has magnitude only whereas velocity has both magnitude and direction. ans5. when we apply a brake,then acceleration is known as the deceleration or negative acceleration. ans6. because acceleration due to gravity acts downwards and hence equations of motions get changed to: put (-g) in place of a . ans7. v->final velocity u->initial velocity a->acceleration t->time ans8. use s=ut+a/2(t^2) ans9. in 40 sec completes one round of cicular track i.e. 2*3.14*100 = 628 m in 2 min(120 sec) completes two round of cicular track i.e. 2 * 628 =1256m in 2 min 20 sec(140 sec) completes two and half round of cicular track i.e.1256 + 314=1570m hence distance covered is 1570m. now for displacement,in 2 min 20 sec,athelete is on the other endpoint of the diameter, so displacement is 200m i.e.diameter of the track. ans10. (i) easy to represent. (ii)can get certain things directly.
Answers:Okay so Keq is a constant (equilibrium constant) Reactions don't run to completion and most reactions also occur in the reverse direction. Basically an equilibrium exists at which point the rate of the forward reaction equals the rate of the reverse reaction. So your not changing the concentrations of reactants or products but your basically still having a reaction occurs that just happens to be equalized on both sides. (DYNAMIC meaning still occuring) Keq = the concentration of products (raised to their coefficients) /the concentration of reactants (raised to their coefficients) aA + bB <=========> cC + dD say that's a reaction in which the lower case letters represent the coefficients of a balanced reaction The double arrow indicates a reaction that reaches equilibrium. Which means that while A + B are converted to C and D. C and D are being converted to A & B at the same rate. Okay so this is equilibrium in its general sense. Now with acids and bases. There are things known as strong acids and strong bases which are considered to run to completion and dissociate 100% in water. HCl Hydrochloric acid for example a common strong acid (of the stomach) will completely lose its hydrogen (the entire solution) making it a strong acid Calcium Oxide is a strong base will completely dissociate also. ____________________ However with these strong acids and bases there are also some weak acids and bases And that means they don't dissociate 100%. SO there is an equilibrium Have you heard of acetic acid? CH2COOH CH2COOH <======> CH2COO- + H+ as you can see there is an equilibrium meaning that while some of the acid is dissociating. some of the CH2COO- is combining with the H+ to form CH2COOH. So if you could isolate the individual molecules in an acetic acid solution you would see CH2COOH, CH2COO-, and H+ ions floating around However if you isolated a HCl solution. You might only see H+ and Cl- ions Same thing goes with bases. weak bases will only slightly react in water NH3 + H2O <======> NH4+ + OH- Ammonia is a weak base. Okay so now Ka and Kb are basically equilibrium constants directed specially for acids and bases Ka = products/reactants let's take a simple weak acid HF (Hydrofluoric acid) HF <======> H+ + F- the Ka for this reaction will equal Ka = [H+][F-]/[HF] Now technically this actually occurs in water the correct equation is HF + H2O <======> F- + H3O+ Looking at this complicated equation you can see that the H+ is replaced with Hydronium ion (H3O+) That's basically what happened. In solution it actually looks like a beefed up water molecule however for simplicity sake we just say H+ ions. and the Ka = [F-][H3O+]/[HF] remember water is a liquid and with equilibrium solids and liquids are ignored. Okay so once you understand that Kb is the equilibrium constant for base Kb = products/reactants try for ammonia Kb = [NH4+][OH-]/[NH3] OH btw is Hydroxide ion which bases tend to produce in water. Okay so now we've gone through that. Let's take a look at Kw Kw is the autoionization constant of water. Water actually undergoes a ionization reaction (auto) 2H2O <======> H3O+ + OH- Two water molecules can produce a hydronium ion (H+) and a hydroxide ion. Now if this reaction actually occured to completion we'd be in some serious trouble consuming so much H+ ions. However Kw = 1 E-14. The equilibrium lies way to the left. I think there's a billion water molecules or something before you find one H+ concentration. Kw = [H3O+][OH-] since Kw is a equilibrium constant we can write an equation that denotes it as such. And water is ignored because it is a liquid As you can see if a certain amount of H2O dissociates into H3O+ and OH- then equal amounts of Hydronium and hydroxide are produced water is a neutral solution with a pH of 7. This comes from the fact that the hydronium concentration is 1E-7 okay Ka does tell you acid strength. Larger Ka means that the reaction will produce more product and acids that dissociate more are stronger acids there larger Ka values are stronger acids and larger Kb values are stronger bases by the same logic Water is NOT always have the same equilibrium constant it actually varies with temperature as does any equilibrium constant. So an equilibrium constant is constant as long as you don't change the temperature. Ksp is a solubility product Basically it will allow you to calculate how much product has dissolved from a compound that is slightly soluble in a solution Ksp = products the reactant is a solid so we ignore solids in the equation. Hopefully this rekindles your memory about chemistry.
Answers:Anything will help..Try rewriting your notes on flashcards...then you have them compact so you can utilize them anywhere you find yourself with TIME!..Is there anyone in your class you can study-buddy? Go to the library at your University & check out if they have any past tests filed away as reference materials. You never know. If you can hire a study coach, do it NOW! I'm proud of your accomplishments & wish you much more continued succes. You can do this. Tell yourself that you will PASS. I found that students who walked into my classroom & said I'm going to fail did! Condition your spirit & your mind will follow.