Recent content by hiuting

Homework Statement The sound level in a noisy classroom is 101 dB. How much energy in J is transmitted to the outside through an open window of height 2 m and width 2.75 m, if the class is 40 minutes long?. What is the decibel rating 1 km from the classroom, assuming sound is distributed...

oh right. correction!

Well according to my knowledge, in rotational kinematics, acceleration is perpendicular to the velocity. Therefore it should be centripedal acceleration.

Homework Statement The A-string (440Hz) on a piano is 38.9cm long and is clamped tightly at both ends. If the string is under 667-N tension, what is its mass?Homework Equations \lambda = vT \mu = mass/length v = \sqrt{F/\mu}The Attempt at a Solution I don't really know which equations to useI...

Homework Statement 100mL of 0.10M HNO3 was added to a 100mL mixture containing 0.30M acetic acid and 0.10M sodium acetate. Ka = 1.8 x 10-5 Homework Equations CH3COOH \rightarrow H+ + CH3COO- CH3COONa \rightarrow Na+ + CH3COO- CH3COO- + H+ \rightarrow CH3COOH The Attempt at...

then v1 final and v2 final are the same??

Homework Statement I'm confused about when to use which formula. I thought for inelastic collisions, for example, when a bullet is shot into a block, I should use (mbullet)(vinitial) = (mbullet + mblock)(vfinal) but it turns out that I must use why do i have to use this one...

Start with: Wnc = \DeltaK + \DeltaU for part 1, you are looking for Vf this gives you... -(0.21)(37.8)(7.96) = (1/2)(4.5)(Vf2) - (4.5)(9.8)(4.1) turns out that Vf is 7.23m/s .. tell me if it's right. for part 2, you are looking for [B]s, the distance you use the same: Wnc =...

This involves energy right? So kinetic and potential energies have to be considered. (I just finished learning this, so I might be wrong) :) Looks like a webwork problem to me... :D

Homework Statement I don't know when the work of a spring is negative, and when it's positive... When is the work of a spring negative and when is it positive? Homework Equations Wsp= -(1/2)(k)(xf2-xi2) The Attempt at a Solution I can get Wsp to be positive when the spring is...

thanks :) I can't believe I didn't think of that.

Homework Statement Why does the chemical reactivity increase as we go down in a group? Homework Equations none The Attempt at a Solution I know it has to do with the atomic radius... but I'm not sure :P

I'm not really interested in calculus, chem, or physics. I mean, I'm doing good in the subjects... but I don't really like any of them. How can I choose a career in the science field if I don't like any of them? I'm soo bored and pressured right now with theses subjects... and even a little bit...

There's a lot of memorization involved. BUT, there's a lot of logic to it too. So spend time really understanding, and you'll do fine. :) i just failed a chem quiz, but that's 'cause i didn't study and didn't try understanding. i don't like memorizing stuff either... and i need to spend a lot of...

you MUST find the components of the velocity... 'cause that's what projectile motions are all about! :) so it should be: vertical component = 35sin52 horizontal component = 35cos52 trick: draw out the picture and you'll see why you should use sin and cos. =)