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# Physics/energy...

Question
I understand physics theory but can't solve physics problems.
Today my teacher asked me a question, that is.....
A motorbike start a race at rest.it requires 30 m/s of speed.1 cc petrol is needed to require this speed.if the motorbiker increase speed from 30m/s to 60m/s how much petrol will be needed?
it was a very very simple problem.the ans is
W=1/2 mv^2
or,1 cc=1/2mv^2 (0m/s to 30m/s)
now...the speed is being double. so work will increase 4 times as before.so 4cc petrol will be needed. (0m/s to 60m/s)
so 4-1=3 cc will be needed for 30 to 60m/s
how easy is this! but I couldn't do this...I am very disappointed.what can I do to get rid from such type situation. please help me.....

When you encounter a type of problem in physics that you struggle with, the human tendency when thinking about it is to try to tackle the problem itself.  When you're starting out in physics, this is the first classic mistake.  What you need to do is to gain an understanding of the types of problems through practice.  Look at similar problems, see how they're similar and different, and recognize the ways you would vary your approach to solving these problems.  Then, when you have enough examples to look at a type of problem (in this case, a conservation of energy problem) with some confidence, thinking about an individual problem will give you a deeper understanding of the detailed physics.  It seems that I'm putting the cart in front of the horse, recommending this approach, but it's more naturally like how we learned mathematics.  First we learned to count, as children, by memorizing.  A deeper understanding of numbers followed later.  Unfortunately, no one teaches children basic conceptual physics and so adults struggle when they first encounter it the way they would struggle if they first learned Chinese (assuming they're born and raised somewhere that Chinese is not spoken).  You should also avoid the second classic mistake, working alone.  Go through a discussion of the approaches to the problems (just break down the problems, punching the numbers into a calculator is a waste of time initially) with someone else who is comfortable with them and discuss how you would solve the problem.  That gets you through experience with ten times as many problems without the frustration of actually solving them, which makes solving subsequent problems an easy and even fun experience.  Trust me, physics is far more fun if you find it easy to solve, and that comes through this type of practice.

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.