<p>Halliday and Resnick is mediocre, its only good parts are the example problems that they cribbed from The Flying Circus of Physics (a book that I <em>do</em> recommend). The Scientists and Engineers book is better but in all honesty the best intro physics book for a two or three-semester sequence is either Cutnell and Johnson or the Physics of Everyday Phenomena. Too bad both are non-calc.</p>
<p>bschoolwiz, I’m genuinely curious (which is why I started the thread), could you tell me what those problems were and what the wrinkles were?</p>
<p>I’ve gotten by with young and freedman’s university physics so far. Get to try Knight’s physics for scientists & engineers in the fall.</p>
<p>Tom: Well, one of the problems on our review sheet was a tension problem where you have a beam 2 m long running horizontally and attached to a vertical wall on the left by a hinge- then there is a string running from the top of the wall down to the midpoint of the beam at 55 degree angle(FT), then one block of mass is hanging directly down from the midpoint of the beam and one other block of mass hanging down from the right edge of the beam( at the 2m mark)</p>
<p>I tried to solve it as any tension problem given in class but the professor told us that in order for us to solve it, we would have to approach it as a torque problem using the point where the beam and the wall attach as the pivot. I was like ***?</p>
<p>So basically, (1) FT sin (55) = m1* g* (distance from pivot) + m2 *g ( distance from pivot)</p>
<p>So we find FT- then he asked us to find the direction and magnitude of this FH(Force supplied by the hinge). </p>
<p>I was not even able to visualize this FH, but he told us to draw a free body diagram with the FT pointing toward the wall(the string) and the FH arrow pointing the opposite direction away from the wall as if they would meet like a triangle.</p>
<p>After doing that, we established that FHx cos 55= FT cos 55 and FHy = FT sin 55. We plug in FT for both and Find the x and y elements of FH.</p>
<p>So basically, FHx becomes your i-hat coordinate and FHy is your j hat coordinate, you draw the two vectors and then connect the resultant- that will give you the magnitude of this FH. then to find the angle, it is just a matter of doing arctan(FHy/FHx) and we find the angle haha.</p>
<p>This is a bit of an extreme example but I guess what frustrates me more than anything is not being to even see or visualize stuff like this FH and understanding how to incorporate it into our free body diagram</p>
<p>It seems your problem is in your approach, as there always tends to be something important you miss.
Do you do plenty of practice problems? In any physics-based classes I’ve ever taken (the physics series, fluid mechanics, etc), a solutions manual is very helpful (really hard to succeed without one, really, unless you don’t value your own time) because you get a much better understanding of how to apply methods. Tests usually feature a heavily simplified version of homework problems that tests the concepts in a simple but new way.</p>
<p>That’s a straight forward statics problem, it sounds like your physics professor’s teaching style isn’t clicking (which is very typical of physics profs). You won’t really need the concepts for IE anyway, so do your best and move onto the cool applied math (markov chain, stochastic matrix, etc).</p>
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<p>Well, I guess if you didn’t see right away that that was a balance of torques problem then I can see your difficulty. 
The beam pivots on its hinge and both the string and gravity are exerting opposing torques on the beam about that hinge (and the tensions from the hanging weights). Since the bar ain’t accelerating rotationally or linearly that leads to two or three equations right away: net torque equals zero and so does net force in both horizontal and vertical directions.</p>
<p>Yeah, I remember being a little thrown the first time we had to find this mysterious force from a hinge. One way of handling it if you can’t figure out which way it is pointing is to just break it into horizontal and vertical components. One will exert a torque, t’other won’t, in this case.</p>
<p>And da6onet, physics has PLENTY of cool applied math. :P</p>
<p>At my engineering college, Physics was considered the “freshman flunk course”. It required more than its fair share of study time, and many students only passed due to the curved grading. (Phew - I had AP physics credit and only watched their pain - my sophomore statics class was easier.) </p>
<p>In my AP physics class in hs, I found E&M much harder than mechanics. It just didn’t have a way to visually click into my understanding.</p>
<p>I don’t think physics for engineering students is that hard. After all, most engineering students (not counting physics/engineering physics majors of course) only have to take what is equivalent to Physics B+C, and for some engineering majors perhaps another course which covers topics like waves, fluids, etc. After that, they take engineering classes which apply the fundamental physical concepts to specific engineering problems, like circuits for EE’s, statics for ME’s, and so on.</p>
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Reaction forces are defined by the motion they constrain. Just draw the components of any reaction force and work back to the direction.</p>