Helpful ways to tackle solving problems

[jg871]

I'm taking a big physics test tomorrow, and I am certain if I took it right now that I would be in trouble. I look over each problem set and I draw blanks, but when the instructor starts one and draws a sketch along with listing the knowns and unknowns, I realize how to do it. Are there any helpful websites to practice some introductory physics problems? My biggest weakness comes to anything involving vectors, along with figuring out magnitudes/directions of them.

 

[kreil]

When you do find some practice problems, try to apply these general steps. It's just a solid process for solving any physics problem. You can probably find quite a few right in these homework forums!

1. Write down all of your known quantities, and any unknown quantities you're interested in.
2. Draw a picture to represent the problem. Make sure to clearly label all of the forces and vectors mentioned in the problem. If you're drawing vectors, make sure you label your directions as well (the positive x and y axes). The picture is complete if you can also add the unknown quantity so that you know what you're solving for.
3. Write down any relevant equations.
4. Use your picture and equations along with your known values to solve for the unknowns. Sometimes you'll have to use the picture to properly apply the equations. Other times you'll have more information than you need, or you'll have to solve intermediate problems to get where you want.

 

[homo-sapiens]

For physics problems i would suggest using google. I would think there would be a LOT of introductory problems out there.
For tips for tackling problems, Staying clam for me is a very important since being hot headed and rushing through things will tend to produce more mistakes. kriel above pretty much said all that is needed to be said when doing vector problems.
One more, if you are doing vectors, you need to review trigonometry FIRST! You can't do vectors without any knowledge of cos, sin and tan. ( oh yeah, Pythagorean theory is a need-to-know too when combining x and y components into final vectors)

 

[CWatters]

when the instructor starts one and draws a sketch along with listing the knowns and unknowns, I realize how to do it.

Perhaps that's a clue :-)

 

[Simon Bridge]

You should find someone to talk to in person - someone to watch you do a problem so they can see where you get stuck.

From your description, you know about reading through the description and making a list of everything that has a number (giving a letter to each number) and also identifying the unknowns... is that correct?

The place people tend to freeze is when they start a problem but do not know the correct way to solve it... it's like there is some force stopping you writing anything down and your mind goes all white and numb. Is that what you experience - thereabouts?

 

[jg871]

You should find someone to talk to in person - someone to watch you do a problem so they can see where you get stuck.

From your description, you know about reading through the description and making a list of everything that has a number (giving a letter to each number) and also identifying the unknowns... is that correct?

The place people tend to freeze is when they start a problem but do not know the correct way to solve it... it's like there is some force stopping you writing anything down and your mind goes all white and numb. Is that what you experience - thereabouts?

Yes, absolutely.

 

[Simon Bridge]

The place people tend to freeze is when they start a problem but do not know the correct way to solve it... it's like there is some force stopping you writing anything down and your mind goes all white and numb. Is that what you experience - thereabouts?

Yes, absolutely.

... I figured as much.

What you are experiencing is a form of fear.
Most often it comes from earlier in your education where you have been criticized or even punished for starting out on the wrong path r wasting paper or something. Maybe there is also an element of not wanting to look stupid in front of your friends sort of thing.
It can be hard for pin down - but it is fear all the same and you don't have to let it master you.

The first step in mastering a fear is to name it:
You don't like to write things down before you know what you are supposed to write down.
It's like there's a wall in the way. You need to get past that wall.

The trick is usually just to start writing things down - anything: force your hand to move.
The first thing to do is reread the problem statement - every time you see a number, write it down and give it a letter.
You don't need your analytical mind for this so just switch it off - ignore it. It's purely mechanical: see number - write it down - give it a letter for a name - a machine can do it. There is no possible way to be wrong about this. You may miss some out - doesn't matter, you'll find out soon enough.

As you do this, a picture should start to form in your head. The part of your mind that normally worries and freezes you up will do this automatically once you start writing the list. So sketch out that picture.

(You may prefer to do it the other way around - whichever seems to come the easiest - i.e. if the problem involves a circle of some kind: draw a circle, that's easy! May turn out to not matter - never mind ... just start adding details as the description comes together - start drawing from the end of the first sentence.)

Once you've got a list of knowns and a picture, you need to give the unknown you need to find a name too.
Then you can switch that pesky part of your mind back on to think about the problem now it's all laid out neatly.

The rest is practice - the most important thing is to get used to writing things down before you know how to solve the problem.
It is the same for pretty much everyone who looks clever - they just hear about a prblem and immediately start working on the solution: it's like they have figured out how to do the problem within seconds right?

It's a trick - they have started work before they know what the right way to do the problem is.
Often they have not seen what to do until they are about half way.

Good problems to work on for this skill are kinematics and ballistics - it is the main reason for making you learn them.
There's lots online and you can make up your own.

Remember, lots of people have had to do this before you.

 

[jg871]

... I figured as much.

What you are experiencing is a form of fear.
Most often it comes from earlier in your education where you have been criticized or even punished for starting out on the wrong path r wasting paper or something. Maybe there is also an element of not wanting to look stupid in front of your friends sort of thing.
It can be hard for pin down - but it is fear all the same and you don't have to let it master you.

The first step in mastering a fear is to name it:
You don't like to write things down before you know what you are supposed to write down.
It's like there's a wall in the way. You need to get past that wall.

The trick is usually just to start writing things down - anything: force your hand to move.
The first thing to do is reread the problem statement - every time you see a number, write it down and give it a letter.
You don't need your analytical mind for this so just switch it off - ignore it. It's purely mechanical: see number - write it down - give it a letter for a name - a machine can do it. There is no possible way to be wrong about this. You may miss some out - doesn't matter, you'll find out soon enough.

As you do this, a picture should start to form in your head. The part of your mind that normally worries and freezes you up will do this automatically once you start writing the list. So sketch out that picture.

(You may prefer to do it the other way around - whichever seems to come the easiest - i.e. if the problem involves a circle of some kind: draw a circle, that's easy! May turn out to not matter - never mind ... just start adding details as the description comes together - start drawing from the end of the first sentence.)

Once you've got a list of knowns and a picture, you need to give the unknown you need to find a name too.
Then you can switch that pesky part of your mind back on to think about the problem now it's all laid out neatly.

The rest is practice - the most important thing is to get used to writing things down before you know how to solve the problem.
It is the same for pretty much everyone who looks clever - they just hear about a prblem and immediately start working on the solution: it's like they have figured out how to do the problem within seconds right?

It's a trick - they have started work before they know what the right way to do the problem is.
Often they have not seen what to do until they are about half way.

Good problems to work on for this skill are kinematics and ballistics - it is the main reason for making you learn them.
There's lots online and you can make up your own.

Remember, lots of people have had to do this before you.

I appreciate your insight, the problems I'm having really fit in with what you are referring to. I'll take your advice and thank you.

 

[Simon Bridge]

A sympathetic tutor can help too.
Another good way to go is to hep out here.
Go to the introductory physics homework section and look for people to help.
There is a good chance there are a few who are struggling with something you have done recently - read through their problem and see if you can do it yourself. Then see if you can work out how to lead them to the solution without actually telling them how to do it.

When I'm doing that, I don't bother to solve the problem myself ... I don't need to know the answer in order to know which way to go to find one. But actually doing the problem will be a good exercise for you. If you find it tricky - you can watch how others help out.