Gaining a Deeper Understanding of Physics Problems

[MurdocJensen]

The professor and my text aren't exactly doing it for me when it comes to my conceptual understanding of physics. I find myself getting frustrated when it comes to certain problems, mainly because the only thing standing in the way of me getting the right answer is how I set up the problem.

This is not to say I don't get anything from m teacher or text, but I just need another point of view when it comes to considering physics problems.

Go sharks.

 

[russ_watters]

Without a specific example it is tough for us to know what exactly your issue is.

 

[MurdocJensen]

Wow. Blanked pretty hard there.

Ex: When solving potential and kinetic energy problems its always hard for me to know when to use a certain potential or kinetic energy relation. An example would be when I needed to find an increase in gravitational potential energy, and ended up finding it from the work from a spring.

More generally, there seem to be a lot of these small conceptual roadblocks that stop me from getting where I need to go.

It's a pretty sparse description, but what I need are suggestions for texts or online materials that could help me form a more concrete conceptual understanding of physics.

 

[Dale]

An example would be when I needed to find an increase in gravitational potential energy, and ended up finding it from the work from a spring.

You might want to start by paying more attention to units. You should never make this kind of mistake because the units don't match up. It is an easy check that should be an automatic part of solving every problem.

 

[MurdocJensen]

I understand what you're saying, and I check my answers like that often. My issue was with the fact that I found an increase in gravitational potential by finding the work from a spring. Both answers have the same units, but I don't quite 'get' how an increase in gravitational potential was found by calculating the work from the spring in that case.

What I'm really trying to say is that I run into these little mental hurdles that prevent me from going forward with solving a problem. These conceptual pitfalls make the process really uncomfortable and, even when I get the right answer, I don't feel like I've learned a lot.

Dunno. Maybe I'm making no sense.

 

[DThielke]

The key thing to remember in problems like this is that energy must be conserved. All the energy you start with has to go somewhere.

Consider a spring that is compressed and locked with a block on top of it. Because the spring is compressed, it has energy stored in it. When you release the spring, it expands and raises the block. The energy that was originally stored in the spring has now been transferred to the block as potential energy, because by lifting the block, you have done work against gravity.

I'm not really sure if this is what you're looking for, but I hope this helps.

 

[Dale]

Both answers have the same units

No, they don't. The formula for a spring is E = 1/2 k x² where E is in units of J=kg m²/s², k is in units of N/m=kg/s², and x is in units of m. If you attempt to plug in g for k then you should immediately notice that g is in units of m/s² which is different from kg/s².