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Trickstar
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So I acquired an old Physics textbook (Gioncoli Physics 2nd Edition) out of which I am attempting to learn classical mechanics from. It's in Algebra and not Calculus so I thought I could do it since I just completed Advanced Algebra 2 w/ Trigonometry this year. The first chapter is on Kinematics in 1 dimension. So far I understand everything and have been able to do all of the exercises up to an example using uniformly accelerated motion. It is worded as follows:
My technique style of learning is to try and solve for the uniform equations myself from the standard instead of just copying them so I'll learn and the book is really confusing when it comes to explaining things. The book gives the solution and which equation it used, but I don't really understand how it got there. I'll first show the books solution then show my work.
Book's solution:
My work:
I figured that my given variables were a = 12 m/s2 and x = 100 m. After that I figured I was supposed to solve for v:
[itex]a = \frac{v-v_{0}}{t}[/itex]
solves to:
[itex]v = v_{0} + at[/itex]
and plugging in the values it would simplify to:
[itex]v = 12t[/itex]
After this, I plugged into the values and simplified the velocity formula:
[itex]v = \frac{100}{t}[/itex]
Next I balanced the formulas so that I could solve for t, since it was another variable I needed. So:
[itex]12t = \frac{100}{t}[/itex]
simplifies to:
[itex]t = \sqrt{\frac{100}{12}}[/itex]
so then I had the values for t, x, and a:
[itex]v = 100/\sqrt{\frac{100}{12}} \approx 34.641[/itex]
So there's my problem. I don't understand how my solution for v is so different from the books. Thanks in advance for any help. I'm assuming that in an actual physics course I would memorize the basic equations and I'm expected to know how to work out the uniformly accelerated motion equations on the spot, otherwise there would be too many equations to memorize.
Suppose a planner is designing an airport for small planes. One kind of airplane that might use this airfield must reach a speed before takeoff of 200 km/h (55.6 m/s) and can accelerate at 12.0 m/s2. If the runway is 100 m long, can this airplane reach the proper speed to take off?
My technique style of learning is to try and solve for the uniform equations myself from the standard instead of just copying them so I'll learn and the book is really confusing when it comes to explaining things. The book gives the solution and which equation it used, but I don't really understand how it got there. I'll first show the books solution then show my work.
Book's solution:
We use eq. 1-10c ([itex]v^2 = v_{0}^{2} + 2a(x - x_{0})[/itex]) with x0 = 0, v0 = 0, x = 100 m, and a = 12.0 m/s2. Then
[itex]v^2 = 0 + 2(12.0 m/s^2)(100 m) = 2400 m^2/s^2[/itex]
[itex]v = \sqrt{2400 m^2/s^2} = 49.0 m/s[/itex]
Unfortunately, this length runway is not sufficient. By solving Eq. 1-10c for (x - x0) you can determine how long a runway is needed for this plane.
My work:
I figured that my given variables were a = 12 m/s2 and x = 100 m. After that I figured I was supposed to solve for v:
[itex]a = \frac{v-v_{0}}{t}[/itex]
solves to:
[itex]v = v_{0} + at[/itex]
and plugging in the values it would simplify to:
[itex]v = 12t[/itex]
After this, I plugged into the values and simplified the velocity formula:
[itex]v = \frac{100}{t}[/itex]
Next I balanced the formulas so that I could solve for t, since it was another variable I needed. So:
[itex]12t = \frac{100}{t}[/itex]
simplifies to:
[itex]t = \sqrt{\frac{100}{12}}[/itex]
so then I had the values for t, x, and a:
[itex]v = 100/\sqrt{\frac{100}{12}} \approx 34.641[/itex]
So there's my problem. I don't understand how my solution for v is so different from the books. Thanks in advance for any help. I'm assuming that in an actual physics course I would memorize the basic equations and I'm expected to know how to work out the uniformly accelerated motion equations on the spot, otherwise there would be too many equations to memorize.