# Courses Learning Physics as 9th grader + precalc test out

1. Mar 5, 2017

### InventorX

Hello! I am in 9th grade and I am really interested in physics. I got this book from my uncle on my birthday but it says there is calc in it: https://www.amazon.com/University-Physics-Modern-14th/dp/0321973615

I can't give it back because its disrespectful in my culture. Can I still learn from this, or should I just wait till calc (currently in H.geometry) ? Is it possible to learn the calc as you go along or is it just too much?

I also wanted to ask if you would recommend testing out of precalc into calc BC. Is it possible to learn precalc while going through H.alg 2 w.trig or is it better just to take the class? A lot of people at my school say they wished they skipped it while others say the opposite. Thanks for your time and have a nice day.

Last edited by a moderator: May 8, 2017
2. Mar 5, 2017

### Staff: Mentor

I think you can learn calculus on your own to do physics problems as the derivatives and integrate are fairly simple to compute.

I did that when I was in 12th grade where I had a background in trig, series and sequences. Truthfully I understood the concepts pretty well but at the time skipped over the limit stuff. However limits in themselves are important to understand and will help in higher level math.

I also thought it was cool to skip the first course in calculus and convinced the prof that I knew the stuff except for the limits. I did well in the followon classes but a year or two later on realized that taking the class would have been an easy A (and probably boring) and I would've had time to prepare for future courses.

3. Mar 5, 2017

### Staff: Mentor

To see how difficult it might be check out these videos online at:

Www.Mathispower4u.com

The two key concepts in calculus are that the derivative of a function gives you the slope at each point on the function. If you take the derivative of a line you'll get its slope.

If you integrate a function you'll get the area under the curve. If you again consider the line and integrate its equation you'll get the area of the triangle made by the line and the x axis.

4. Mar 5, 2017

### InventorX

Thanks for the response, and just to clarify, learn the calc first and then start the textbook?

5. Mar 6, 2017

### Staff: Mentor

I would say, go ahead and start with that physics book and see how it goes. I've never studied or taught from that book myself, but the books at that level that I have used, introduce basic calculus concepts when needed, both for students who have not seen them before, and as a review for students who have seen them already. The calculus is used mainly in a conceptual way, to simplify the notation and make it more general. So the most important thing is to get a good conceptual understanding of what derivatives and integrals mean in various physical situations.

A calculus textbook derives things (more or less) rigorously, and teaches techniques for calculating complicated derivatives and integrals. An intro physics book generally sticks to examples that use simple derivatives and integrals, so as to focus on the physics.

For day-to-day work while studying intro physics, it's far more important to be fluent in algebra and basic trigonometry. For algebra, you need to be able to work symbolically, not just numerically. Here's what I mean by this: In a typical high-school algebra class, you might be given an equation such as $3x + 1 = 10$ and asked to solve it numerically to get $x = 3$. In a physics exercise, you're more likely to start with an equation such as $ax + b = c$ and need to rearrange it to get an equation for x: $x = (c - b)/a$. And then you might have to combine this with something like $c = 2b +a$ and get a single equation for x in terms of a, b and c.

(I've actually had college students ask me, when faced with something like the above, "How do I solve for x? There aren't any numbers!" )

For trigonometry, you need to be familiar with the basic definitions of trig functions with respect to a right triangle: sine = opposite/hypotenuse, etc.; and with some of the basic relationships between them, e.g. tan θ = sin θ / cos θ. You need this to work with vectors and their components.

Don't let all this detract from your official classes. You need to do well in those. Make them your first priority, and use only your spare time for trying to "get ahead" in physics.

Last edited: Mar 6, 2017
6. Mar 6, 2017

### InventorX

Thank you for your response. I was just planning to learn it over the summer along with some other stuff like C++ and electronics. Thanks again for the response I will try and muscle through it and pick up some calc stuff on the way.

7. Mar 6, 2017

### Dr. Courtney

Coursera Calculus One will likely provide all the calculus needed for that book. It is an online course. Free.

Most students should take precalc. The extra algebra practice is very valuable. Most STEM majors use algebra more than calculus in college AND in their careers.

8. Mar 6, 2017

### Staff: Mentor

Read through the book first and see if there are actually any questions or problems which require you to know calculus. It may be that the book simply derives things in calculus but doesn't require you to use calculus to solve problems. And there's certainly nothing wrong with just doing the problems that only require algebra and avoiding any requiring calculus.