Why is Physics So Hard? Advice to Improve

[jmason52]

Not sure if I heard this in a movie or read it somewhere, but somehow, it just seems to fit:

Why is Physics so hard? Cause if it was easy then anybody could do it.

 

[Shackleford]

My mechanics professor asked us how we know who is a physicist. He said it's the one who spends the most time looking at a problem.

 

[NeedsHelp1212]

update: halfway through the 2nd marking period I had an A+ (98). Got a 41/50 on the last quiz so i dropped to a A (96) but hopefully with tomorrow's quiz which is on heat i can get back to an A+. Thanks for all the motivation guys.

 

[The_Duck]

Exactly, I have no problem solving for a variable. Too bad the problems don't simply give you the numbers needed to plug into the equation.

Perhaps you don't feel like expending any more mental effort than you have to, but you will "get" physics at a deeper level if you look beyond finding the numbers to plug into equations. For instance, learn /why/ the equations are true and don't take it on faith that, for instance, "distance traveled = (1/2)*acceleration*time^2 + (initial velocity)*time."

 

[cristo]

How can you get an A+; surely an A should be the best grade? American education confuses me...

Anyway, I think if your main concern is that you got an A-/B+ when you really 'expect' an A, then you have nothing to worry about!

 

[Dembadon]

How can you get an A+; surely an A should be the best grade? American education confuses me...

[...]

I've never taken a class in the U.S. where an A+ < 100%. I earned an A+ (105%) in English Literature, but that's because the instructor offered some extra credit. I've never had a math or science course that's even offered extra credit assignments. If one wants extra work, one can take an honors course, which I think is much more valuable than an A+.

 

[NeedsHelp1212]

How can you get an A+; surely an A should be the best grade? American education confuses me...

Anyway, I think if your main concern is that you got an A-/B+ when you really 'expect' an A, then you have nothing to worry about!

Let me re-state I am in high school NOT college. In a typical american high school an A+ is in the range from a 97 to a 100. An A is in the range from a 93-96. An A- is a 90-92. A B+ is an 87-89, B is an 83-86, B- is an 80-82 and so forth until you reach an F.

And my main concern actually was that physics would get harder as the year progressed and my grade would drop lower and lower. Well as of this point the exact opposite has happened. I have looked ahead at future chapters and the topics seem kind of hard (mirrors and other "weird" physics topics- I am so used to physics being just about motion). Hopefully i can continue to understand the material!

 

[Dembadon]

Let me re-state I am in high school NOT college. In a typical american high school an A+ is in the range from a 97 to a 100.

[...]

I've never seen this, nor does it make sense to me. *shrug*

 

[Chunkysalsa]

My HS never did A+, not like I'd get them cept my computer classes.

 

[nlsherrill]

Well, physics is "easy," but the math required to do some physics problems is quite hard. In other words, solving particular problems involves solving very complicated mathematical equations.

I don't really agree with this. Math is not why physics is hard, but sometimes physics has quite complicated mathematics as well. Every single problem except maybe 2 that I solved this semester(University Physics 1) was not hard because of the math.

 

[iRaid]

I'm in hs now and we can't get A+'s wtf..

 

[NeedsHelp1212]

lol are you guys serious? How does your grades then get converted to GPA? For us in regular classes (which physics is considered as a regular and is my only regular class, the rest being honors and AP which actually give you the chance to have a higher than 4 GPA). Anyway, a regular class with an A+ for us translates obviously into a 4.0. An A is a 3.7, A- is a 3.3 and so forth. Let says you are in AP history and get an A- (3.3). That really goes in as a 4.3 because the AP gives it a one point curve. I was under the impression all high schools do this and have A+'s but i guess not?!?

 

[NeedsHelp1212]

hey everyone, i have midterms in this class tomorrow. Wish me luck! I have been studying all day. Once again thanks for all the encouragement and help I have gotten from this thread

 

[lisab]

hey everyone, i have midterms in this class tomorrow. Wish me luck! I have been studying all day. Once again thanks for all the encouragement and help I have gotten from this thread

Good luck!

 

[oddcitations]

hey everyone, i have midterms in this class tomorrow. Wish me luck! I have been studying all day. Once again thanks for all the encouragement and help I have gotten from this thread

You'll do wonderfully!

 

[Angry Citizen]

I don't really agree with this. Math is not why physics is hard, but sometimes physics has quite complicated mathematics as well. Every single problem except maybe 2 that I solved this semester(University Physics 1) was not hard because of the math.

It's not physics or math that's hard. What's hard is setting up the problem. You can run through disgustingly long and complicated integrals like they were 1+1, and still get knocked on your butt by physics math that is often simple arithmetic.

Physics is not a formula-based activity. You can't memorize your way through physics like you can with chemistry, biology and the like. You have to understand the conceptual difficulties in the problem, then translate that concept into another language: Mathematics.

 

[Shackleford]

It's not physics or math that's hard. What's hard is setting up the problem. You can run through disgustingly long and complicated integrals like they were 1+1, and still get knocked on your butt by physics math that is often simple arithmetic.

Physics is not a formula-based activity. You can't memorize your way through physics like you can with chemistry, biology and the like. You have to understand the conceptual difficulties in the problem, then translate that concept into another language: Mathematics.

This is correct. I discovered this just last semester in my Classical Dynamics course with an exceptional physicist. We covered quite a bit of a material. He gave us the hardest problems from the newest Thornton and Marion book. The hardest part was just getting started on the problem, i.e. setting up the problem.

 

[loadshare]

Study harder..never give up

 

[Ryker]

This is correct. I discovered this just last semester in my Classical Dynamics course with an exceptional physicist. We covered quite a bit of a material. He gave us the hardest problems from the newest Thornton and Marion book. The hardest part was just getting started on the problem, i.e. setting up the problem.

Well setting up the problem is physics and mathematics. It's not as if you somehow set it up and *then* go do physics and maths. You can't just arbitrarily separate those parts/steps that make a whole.

 

[Shackleford]

Well setting up the problem is physics and mathematics. It's not as if you somehow set it up and *then* go do physics and maths. You can't just arbitrarily separate those parts/steps that make a whole.

How didn't you take that meaning from my post?

 

[nobahar]

Physics is not a formula-based activity. You can't memorize your way through physics like you can with chemistry, biology and the like. You have to understand the conceptual difficulties in the problem, then translate that concept into another language: Mathematics.

Your referring to Secondary school Biology and Chemistry, right?

 

[Vectronix]

Mathematics is entirely arbitrary. It does not dictate physical phenomena. However, it's used by physicists as a language to describe physical phenomena quantitatively very precisely. Someone can understand Newton's Laws qualitatively but not be able to express it quantitatively. That's my distinction - a very fine one, I know.

When doing physics problems the maths is physics, if you don't understand that maths then you don't understand the physics.

I agree with both of you simultaneously. :P

I actually think the higher the level of math, the easier math gets. It would have been nice to understand all the math when I took all of my physics classes in school.

 

[nlsherrill]

It's not physics or math that's hard. What's hard is setting up the problem. You can run through disgustingly long and complicated integrals like they were 1+1, and still get knocked on your butt by physics math that is often simple arithmetic.

Physics is not a formula-based activity. You can't memorize your way through physics like you can with chemistry, biology and the like. You have to understand the conceptual difficulties in the problem, then translate that concept into another language: Mathematics.

Yes, and generally this is fitting to a physics problem. Setting up the problem IS the physics. Setting it up is recognizing which physical laws are/are not conserved, where your limits extend, etc, and then developing a mathematical model to represent it. And this is why physics is hard, because you have to come up with a clever way to even get started on some problems.

I think we are on the same page, but in my opinion "setting up the problem" is the physics part of the problem.

 

[Ryker]

How didn't you take that meaning from my post?

I thought you agreed with the part of Angry Citizen's post that said

"It's not physics or math that's hard."

I guess I should've quoted him instead then.

Yes, and generally this is fitting to a physics problem. Setting up the problem IS the physics. Setting it up is recognizing which physical laws are/are not conserved, where your limits extend, etc, and then developing a mathematical model to represent it. And this is why physics is hard, because you have to come up with a clever way to even get started on some problems.

I think we are on the same page, but in my opinion "setting up the problem" is the physics part of the problem.

And yeah, this is what I meant.

 

[Shackleford]

I thought you agreed with the part of Angry Citizen's post that said
I guess I should've quoted him instead then.
And yeah, this is what I meant.

Oh, sorry.

I was agreeing with

What's hard is setting up the problem.

Setting up the problem is math and physics.

 

[Angry Citizen]

I tend to differentiate the three. Math, fundamentally, is the techniques used. Addition, subtraction, algebra, integration, differentiation, etc. Physics, to me, is the concepts involved. Problem-solving is not physics. For example, when computing force, math is the multiplication and addition/subtraction necessary to describe the problem, physics is the conceptual basis behind the problem (the various relations between concepts and the concepts themselves that tell you why you're calculating force in the first place), and 'setting up the problem' is essentially bridging the gap between the two. You're translating physics into math.

Just my perspective. Doesn't really matter.

 

[Nikitin]

It's not physics or math that's hard. What's hard is setting up the problem. You can run through disgustingly long and complicated integrals like they were 1+1, and still get knocked on your butt by physics math that is often simple arithmetic.

Physics is not a formula-based activity. You can't memorize your way through physics like you can with chemistry, biology and the like. You have to understand the conceptual difficulties in the problem, then translate that concept into another language: Mathematics.

Maybe biology but sure as heck not chemistry (speaking about 2. grade/12. grade (17 year olds) level)

I definitely agree about your math/physics comment. Physics simply uses math as a language, so usually the math is fairly simple.

At first I had real problems adjusting to "thinking physics", but after a while I am OK with it and getting good grades.

 

[NeedsHelp1212]

well I felt like i did OK. It was not easy but it was not terribly hard. Every multiple choice question was tricky in some way, and there was a couple that i had to guess on (these were not the math ones actually). For example, one of the questions had 3 boxes and said if all boxes were pulled with the same magnitude of force F on which box would the kinetic friction be the greatest? The least? And one of the boxes was being pushed horizontally, another was being pushed with an angle forward. So from those 2 the first one would have more friction b/c the x component on the 2nd one is obviously less. But I am confused with the 3rd box. The force was like coming down from the top left. It made no sense.

Another had a picture of a door and force of the same magnitude applied to different parts of the door. And you had to apply the concept of torque to rank in order from greatest to least in terms of torque. And i knew if its at a 90 degree angle (since u take into account sin 90) it would be at the most. Ohhhhhh wow, nvm... i forgot to take into account distance from the hinge...wow.

So yeah basically there was 25 multiple choice, 3 points each. And then 3 open ended worth a total of 25 points. I think i got all of the open ended right.

 

[Angry Citizen]

For example, one of the questions had 3 boxes and said if all boxes were pulled with the same magnitude of force F on which box would the kinetic friction be the greatest? The least? And one of the boxes was being pushed horizontally, another was being pushed with an angle forward. So from those 2 the first one would have more friction b/c the x component on the 2nd one is obviously less. But I am confused with the 3rd box. The force was like coming down from the top left. It made no sense.

Use your definitions. Kinetic friction is dependent on four things: The mass of the object, the magnitude of local gravity conditions (little g), the coefficient of kinetic friction, and any extra force in the y direction. We know little g is 9.8 meters per second squared (assuming this question wasn't one of those alien planet questions). Do we know the masses of the objects? If not, are they all the same mass? Can we assume that all the coefficients of kinetic friction are the same?

From the problem definition, we know that one of the boxes has extra force in the y direction, while one of the boxes does not. The extra force in the y direction, depending on whether it worked with gravity (pushed down on the box) or against gravity (pulled up on the box), would affect the normal force acting on the box. Use the fact that force is a vector quantity to separate it into its x and y components. For the horizontal force, this is unnecessary because all the force is in the x direction. For the funny one at an angle, you need to separate it into its components using vector algebra.

So, if you have three boxes of equal mass (m1=m2=m3), all of the same material and on the same surface (μk1=μk2=μk3, or in other words all the coefficients of kinetic friction are the same), and they're all in the same gravity field (Earth's), then the only possible difference can come from the direction in which the equal force is applied. Thus, the box with the greatest kinetic friction is going to be the box whose force vector is directed downwards (with gravity, thereby increasing the acceleration, thus increasing the normal force, thus increasing the kinetic friction), and the one with the least kinetic friction is going to be the one whose force vector is directed upward (against gravity, thereby counteracting some of the acceleration, thus reducing the normal force, thus reducing the kinetic friction).

Hope this helps.

Another had a picture of a door and force of the same magnitude applied to different parts of the door. And you had to apply the concept of torque to rank in order from greatest to least in terms of torque. And i knew if its at a 90 degree angle (since u take into account sin 90) it would be at the most. Ohhhhhh wow, nvm... i forgot to take into account distance from the hinge...wow.

Well, think of it this way. Have you ever tried to open a door by pushing near its hinge? Takes a lot more force, huh. Just use that intuition in physics. You've done physics for many years without even realizing it.

 

[NeedsHelp1212]

so the one directed downwards has the most kinetic friction? That's what i put! I kind of figured just using logic if your "pushing" down on something there will be more friction.

For the door one I know exactly what you mean but honestly it was a lot more complex because at one point there was multiple forces acting just at different angles. Well not really complex now but what can you do now

And i screwed up on another problem after someone told me what they did. It's so easy too. They gave you the change in velocity (the car was going West) and the time. So it asked for the acceleration. Obviously just divide the change and without thinking i put 10 m/s^2 West. My friend's right though; since the car slowed down (thats what the problem stated) the acceleration would be in the East direction right? Now i remember that was one of the answer choices. Wow already down to a 94... no way i got an A

 

[Angry Citizen]

That's correct. In order to affect a decreasing change in velocity, the acceleration would have to be in the opposite direction of movement.

 

[Ryker]

Use your definitions. Kinetic friction is dependent on four things: The mass of the object, the magnitude of local gravity conditions (little g), the coefficient of kinetic friction, and any extra force in the y direction. We know little g is 9.8 meters per second squared (assuming this question wasn't one of those alien planet questions). Do we know the masses of the objects? If not, are they all the same mass? Can we assume that all the coefficients of kinetic friction are the same?

From the problem definition, we know that one of the boxes has extra force in the y direction, while one of the boxes does not. The extra force in the y direction, depending on whether it worked with gravity (pushed down on the box) or against gravity (pulled up on the box), would affect the normal force acting on the box. Use the fact that force is a vector quantity to separate it into its x and y components. For the horizontal force, this is unnecessary because all the force is in the x direction. For the funny one at an angle, you need to separate it into its components using vector algebra.

So, if you have three boxes of equal mass (m1=m2=m3), all of the same material and on the same surface (μk1=μk2=μk3, or in other words all the coefficients of kinetic friction are the same), and they're all in the same gravity field (Earth's), then the only possible difference can come from the direction in which the equal force is applied. Thus, the box with the greatest kinetic friction is going to be the box whose force vector is directed downwards (with gravity, thereby increasing the acceleration, thus increasing the normal force, thus increasing the kinetic friction), and the one with the least kinetic friction is going to be the one whose force vector is directed upward (against gravity, thereby counteracting some of the acceleration, thus reducing the normal force, thus reducing the kinetic friction).

Hope this helps.

Hold on, if the force is applied straight downward, then there will be no kinetic friction, since only the normal force will be counteracting the force. You can't have kinetic friction if the force is parallel to the movement (well, there is no movement) and doesn't try and move the box in the direction parallel to the surface.

 

[Angry Citizen]

Hold on, if the force is applied straight downward, then there will be no kinetic friction, since only the normal force will be counteracting the force. You can't have kinetic friction if the force is parallel to the movement (well, there is no movement) and doesn't try and move the box in the direction parallel to the surface.

You're right, of course, but I felt that was pretty obvious given that the problem was about kinetic friction. If the vector is pointed downward while still retaining an x component, and given that the force exceeds the maximum static friction, then my statement remains true.

 

[NeedsHelp1212]

got a 94:) Highest grade in my period :)

 

[Chunkysalsa]

Congratulations, you seem like you've been working hard this year and deserve it.

Do you guys do any E&M stuff, I don't remember doing anything relating to that or optics in High School (but I barely remember high school physics anyway, snoozed to a C).