Homework Help

A roller coaster freewheels down a frictionless track from rest a height h above the ground. At the bottom the track becomes a vertical loop with diameter 2a = 16m. How high above the ground (value of h) must the roller coaster start if it is to reach the top of the vertical loop without lifting off the track? The given answer is 20m. I would have thought that the roller coaster needs to start at a height equal to, or slightly more than, the diameter of the vertical circle at the bottom. Energy at start = energy at end, therefore mgh = mg2a, and h = 2a = 16m. Please help me understand why it is not so. Thank you in advance

A bead slides down the surface of a sphere. Ignoring the initial speed of the bead, define the normal force between the bead and the sphere with respect to the angle of displacement. Given Answer: N = mg(3cosL-2) , L is the angle between the bead and the vertical taken from the centre of the sphere. My answer was N = mgcosL. I don't see how the given answer could have been derived.

The question is The dissociation constant of water is 10^-14, explain what this means using a chemical equation. Heres how I'd answer this. The dissociation of water into the ions H3O+ and OH- is in dynamic equilibrium. The concentration of H3O+ and OH- ions present in 1L of water is said to be 10^-7 each and since Kw = [H3O+][OH-] / [H2O]. Do I even need to say all that bullshit or would I get away with writing [H3O+][OH-] / [H2O] [H3O+] = 10^-7 [OH-] = 10^-7

Heres the question Calculate the heat of formation of methane from the following data: C + O2 CO2 DH = -393kJ/mol H2 + 1/2O2 H2O DH = -280kJ/mol CH4 + 2O2 CO2 + 2H2O DH = -895kJ/mol This is not homework its the kind of question that will be on the test so I need to know how to do it. I know what Hess' law is but I just have no idea how to go about solving this. I'm assuming the final reaction can be reversed and it will be endothermic with a DH of +895kJ/mol but apart from that I'm lost.

My task is to design an experiment to answer the question: How does the force of attraction between 2 bar magnets depend on the separation of the bar magnets. I need to write a method beforehand as we are getting marked on how we conduct the experiment but I'm really confused. I tried looking up the experiment but cant find the method I would need when using these materials. Stand and Clamp Newton meter Bar magnet (x2) Blu-tack Masking tape Ruler Does anyone know the best possible method for this experiment while using these materials? Merged post follows: Consecutive posts mergedDon't worry about this. I figured it out.

Hello, I am writting a report for my teacher and need to know a simple question. When the virus penetrates the cell and releases its RNA or DNA, does the cells ribosome's then build new protien parts, using the cells machinery. Or does the virus inject its own molecular machines? thanks a bunch:-)

Hello, It is my first time post, and its nice to be on the forum. I'm having trouble with a certain biochemistry problem from one of my practice tests. It pertains to a laboratory problem in which a target enzyme that needs to be expressed and crystallized is not being synthesized for some reason. A number of expression vectors have been utilized, but to no result. However, we do have the sequence of the N-terminal tryptic peptide to work from, which is as follows: Asp-Val-Met-Ile-Lys-Arg which corresponds to an mRNA sequence of: GA(U or C)- GU(V)- UAG- AU(U,C or A)- AA(A or G)- (A or C)G(V) where (V) relates to a fully degenerate portion of th…

Hi, I'm currently working on my Chemistry Coursework but all of our grade is from Coursework, there is no exam so we have to find out information and then put it into our own words and do an assignment about it. So for one of our assignments I have to: For B Grade: - Describe the properties of Ionic compounds and link to type of bonding - Describe the properties of covalent compounds and link to type of bonding - Describe the properties of metallic compounds and link to type of bonding - Explain a giant molecular structure and link to boiling points - Explain simple molecular structure and link to boiling points - Identify and draw example of simple and giant mo…

I am studying Forensic Science and I am finding the biochemistry part of my course really difficult to grasp. I am currently stuck on why ethanol is used in cases of methanol poisoning. I no its something to do with Alcohol Dehydrogenase and formaldehyde, but where does the ethanol come into it??? Help please?!?!

Okay so im doing a science fair project on how hot polluted water gets when its exposed to sunlight. one of pollutants is fertilizer which contains nitrates. Now someone told me that that might affect my data, if it does then why? can someone please explain in a way that a 7th grader can undestand

does anyone know where to look up the structure of complexes.... I am after strontium carbonate , sodium nitrate and diaqua calcium sulphate. Any link that would lead to answer to my question will be great. Thanks!.

Standard enthalpy of formation: Species Enthalpy (kJ/Mol) Br(g) 111.9 Br2 (l) 0 Br2 (g) 30.9 What is the standard enthalpy of vaporization of bromine? What is the energy neede for the reaction Br2 (g) ---> 2Br (g), i.e. the Br -Br bond energy?

Heres a practice chemistry test to prepare us for the real one next week. Heres how Id answer the questions Q1) What is meant by the Heat of Formation of a substance? The heat of formation is the enthalpy changed when 1 mole of a compound is formed from its elements Q2) Calculate the heat of formation of methane from the following data: C + O2 CO2 DH = -393kJ/mol H2 + 1/2O2 H2O DH = -280kJ/mol CH4 + 2O2 CO2 + 2H2O DH = -895kJ/mol Not sure what this one means. WHat have those reactions got to do with methane? 3.) Draw an energy profile diagram that illustrates an exothermic reaction and include …

I'm thinking 'no', but that's just an educated guess. Any guidance would be appreciated.

What is the standard entropy change for the each of the following reactions at 25 degrees C? a. 2 Na(s) + 2H20 (l) ----> 2NaOH (aq) + H2 (g) b. NaCO3 (s) + @HCl (aq) ----> 2NaCl (aq) + H20 (l) + CO2 (g) Comment on the sign of: delta r S degrees (sorry, don't know how to represent it?)

I know it is possible to break glass with high frequency sound, but is it possible to achieve the same with ice? Is it to do with finding out the resonant frequency of ice? Any help would be appreciated.

does anyone know how to calcultate the ksp of calcium hydroxide ksp=[Ca][OH]^2? I did a lab experiment and it says to calculate the concentration of OH use the formula Ma x Va = Mb x Vb and to get the conc. of Ca using the reaction Ca(OH)2 ----Ca + 2OH. i also have that the average conc of HCl was .1005 and the concentration of standard NaOH was .0993M and the aliquot of the standard NaOH used is 25 mL and the solution titration aliquot size is 25 mL. I am really confused on how to calculate the ksp with this info... can anyone help?

I need to present an economic-related article to my finance class! But All the ones I find seem to be uninteresting filled with political language that wouldn't appeal to my age demographic... so is there anything actually captivating about an economic-situation, money, trends, money-making... sites??

I have seen brackets by peoples name like lepton, quark etc... what are those?? also some people are moderators and experts how does that happen??

Given four choices... 1. Discuss how advances in molecular biology and genetic engineering have permitted numerous technological advances. 2. Discuss how advances in the development of genetically modified organisms (GMOs) have affected growth rate and yield. 3. Discuss the importance of maintaining the rainforests as a natural resource and what it means to our environment. 4. Discuss why earth's climate is changing (the roles of man, naturally occurring trends, and earth's cycles are considered, and an outlook for what can be expected in the near and distant future is given). Which would be the most interesting? I like them all.

Hi all, I am very new here, this is my first post. My son (11) is in grade 5, and has been given a project to build something hydroelectric that will power a lightbulb. Building the turbines seems fairly straight forward. But, my question is, is it possible to build a generator and transformer? If so, could someone possibly point me in the right direction please? Or, am I headed in the wrong direction? The whole point of this project is to understand how hydroelectric power works, and if the project is not constructed by my son understands hydroelectricity he will still get good marks. However, I would like to work on this project with him. Any suggestions? Thanks, …

I don't know if I'm posting this is the correct area as I'm new to the site but here goes. I am writing a paper for my Comparative Physiology class and it is worth 35% of my lab grade. I've received subsequently higher marks in all of my papers but with this one having such a heavy weight I want to get it just right. I am going to post the abstract to my paper, will anyone who knows scientific writing please critique and give me some pointers as to how to make it better? First, a little background information on the paper. We compared ion osmoregulation of teleost fishes. Specifically one estuarine fish (the mosquito fish or Gambusia affinis) was acclimated to …

Hi. Each human cell contains the gene for how many traits? I know that a cell has chromosomes, on which there are thousands and thousands of genes. Does this mean thousands and thousands of traits can be inherited by the genes in every cell? Merged post follows: Consecutive posts mergedNever mind. I realized it can be thousands, or more, traits! Sorry, I forgot I had to merge my posts.

"How can hydroelectric energy be considered the result of the sun's and gravitational energy?" With gravity, water can fall and turn generators to make electricity. But what does the sun have to do with making the energy? Wouldn't it just evaporate some of the water?

I have an other problem of the same nature now. I have understood the question well but i dont understand what formula should be used for the solution. Answer to the question is 7.579 W/m2 C 19 W Water at 50 C flows inside 25cm diameter tube such that hi 350Wm-2 k-1.The tube has a wall thickness 0.8 mm with thermal Conductivity of 16W m-1 K-1.The outside of the tube loss heat by free convection with hoof 7.6 Wm-2 k-1. Calculate heat transfer cofficient & heat loss per unit lenght to surrounding air 20C.