For the folloing 6 questions, I got completely different (way off) answers from the ones given in the textbook. This is really driving my crazy. I checked my work many times but can't find out what I did wrong. If anyone is interested in physics problems and have the time, I hope you can help me check out whether the answers in the textbook are correct or not, so that I can know if I am correct. I really appreciate for your help! Please Register or Log in to view the hidden image! I am wondering if I am calculating something seriously wrong so that I am getting way off answers for all these questions. I am afraid and frustrated now that I am losing confidence in this topic. Please Register or Log in to view the hidden image! 1) A point charge of +3.8x10^-6 C is placed 0.20 m to the right of a charge of -2.0x10^-6 C. What is the force on a third charge of +2.3x10^-6 C if it is placed 1a) 0.10 m to the right of the second charge? [assuming the second charge is the charge on the right side(+3.8x10^-6C), I got an answer of 7.4N, but the answer is 7.9N ] 1b) where would the third charge experience a net force of zero? [I got an answer of 0.53 m to the left of the -2.0x10^-6C charge, but the answer given is 1.2x10^-2 m [right of smaller charge] ] 2) 4 objects, each with a positive charge of 1.0x10^-6 C, are placed at the coreners of a 45-degree rhombus with sides of length 1.0m. Calculate the magnitude of the net force on each charge. [I got 2.2x10^-2 N and 1.9x10^-2 N respectively, but the answers provided are 8.4x10^-3 N and 1.9x10^-2 N respectively.] 3) 3 charges of +1.0x10^-4 C form an equilateral triangle with side length 40cm. What is the magnitude and direction of the electric force on each charge? [I got an answer of 9.7x10^2N[90 degrees from the line joining the other charges], but the answer provided is 8.9x10^2 N[90 degrees away from the line connecting other charges] ]
4) 2 charges of +4.0x10^-6 C and +8.0x10^-6 C are placed 2.0m apart. What is the field strength halfway between them? [I got an answer of 3.6x10^4N/C toward the 4.0x10^-6C charge, but the answer given is 3.6x10^-4N/C toward the larger charge] 5) A point charge of 2.0x10^-6C experiences an electric force of 7.5N to the left. What force would be exerted on a -4.9x10^-5 C charge placed at the same spot? [My answer is 1.8x10^2N, but the answer given is 1.5x10^5N/C ] 6) Please Register or Log in to view the hidden image! [I got 3.2x10^5N/C , but the answer in the book is 1.8x10^5N/C ]
I know you physictists can calculate these very quickly. Please Register or Log in to view the hidden image! Could somebody help me with 1 or 2 questions? I still can't get the answers in the book! Thanks!
I don't believe it. Unless I made the same mistakes as you on all 6 problems, we have: kingwinner: 6, textbook: 0. That book's well on it's way to a lynching.
I've just done the first two, and got the same as kingwinner both times. The text is clearly wrong for 1b) -it's not hard to see that the answer must be to the left of both charges. The textbook answer to number five is also a no-brainer discard. What's the textbook? Does it have a website? There might have been a horror story during printing (answers from previous edition??) that is corrected online.
Thank you for checking, Pete. You are so nice. "I've just done the first two" <-is that questions 1ab & 2, or just 1ab? I am not sure if the answer to Q2 is wrong or not. For this set of questions, I don't know what the textbook is. They are from photocopied pages from a first year university textbook. =============================================== Can anyone help me with the other questions, by the way? Please Register or Log in to view the hidden image!
No kidding? The textbook is wrong for all the questions? That's crazy. What a textbook... :bugeye: These wrong answers kill my time and confidence in physics. Thanks for your help, anyway! :m:
I didn't work the problems, but books can be wrong. I've run into it before, just notify your professor and have him check it. That way the next edition can correct these errors, which seem to have escaped editing.
I sense dead thread necromancy. Also ignorant veiled insults. Who do you suspect lied, and why do you suspect it?
I suspect kingwinner of deliberately giving wrong so called "book answers" for the reason of getting you people to work on the homework problems of his thats just suspicion, I am not accusing anyone of anything... 5 mistakes in a row in a book? nope...ain't happening.
:bugeye: kingwinner also gave the correct answers that he himself worked out. It happens. Not often, fortunately.
He hasn't got the book in his hand. Just copied pages. I'd guess the answer key is mismatched - wrong edition, maybe, or maybe this was printed off of one of those new computer-era setups that randomizes the given variables within a range on the problem sets.
