Monday, December 7, 2009

Newton's First Law


This is what I learned about Newton's First Law.  Also known as the Law of Inertia, Newton's First Law states that an object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an unbalanced force.  In this scenario, the object has the potential to change direction, slow down, and speed up.  When an object is at rest, the sum of the forces in both the x and y axes equals zero.  When this happens the object is in equilibrium, also known as translational equilibrium. In order to solve many problems where forces act upon objects, you must separate forces into x and y components.  This is important when forces, including gravity, act upon the object at an angle other than 0, 90, 180, 270, or 360 degrees, where the force would not be associated with an axis.  In order to find the resultant vector you use the Pythagorean Theorem (R=sq. rt. (A^2 + B^2).  Substitute A and B with Sum of the X and Sum of the Y.  To find the direction of the force you use the equation tan^-1 (Sum Y/Sum X)*absolute value.  Using the calculated Resultant Force you can find the mass by Fg = mg.  I also learned that the Equilibrant and Resultant Forces have the same magnitude and mass, but are in the opposite directions (a difference of 180 degrees).  This is what I have learned about Newton's First Law, Inertia, and Forces acting upon objects.

What I have found difficult about what I have studied is setting up the equations to find the x and y components of forces.  I need to develop more skill in this area so that I can be more time efficient.  Whenever I stumble upon a problem, I always have to stop and go through my SOH CAH TOA, and see which one makes sense.  This process takes me more time than I would expect of myself, and commonly after I finish the problem I second guess my work, or feel uncomfortable.  Whenever I am required to find the x and y component of gravity I have to analyze the force very closely.  Also, whenever I am given an angle of a force in a problem I am forced to think of which angle is actually relevant to the problem.

I feel that my problem-solving skills are generally pretty good.  I often find myself getting frustrated, setting aside the material, and then coming back to the work where I have an epiphany, or an "AhHa!" moment.  From then on, I try to build my confidence and I commonly make up my own problems, or re-do the problems in the homework or class work.  I feel that I help myself understand the problem further by making myself visuals such as FBD's or other sketches.  I have a hard time memorizing equations with variables, and I have found a way that has made me be successful.  Whenever I am introduced to a new equation, I take a few minutes to look at the equation and try to understand its purpose, meaning, and why it works.  By doing this, when I am introduced to a foreign style of problem I have a higher chance of knowing which equation to use.


The physics we are learning in class can be transferred into our understanding of our natural world around us.  Engineers use physics and Newton's laws when designing tables, lifts, and motors.  The engineers must calculate the strength of the material or device in order to build a special race car, cable-stayed bridge, or a hydraulic car lift.  Also, when we are in a car crash our bodies want to continue in our current direction, when there is another force causing the car to slow down, speed up, or change direction.  It is this abruptness that causes injuries in car wrecks due to whiplash, and sudden changes in velocities.  When I walked into school this morning, I opened a door applying pressure as far from the hinge as possible because then the force would be the most effective.

Monday, November 9, 2009

Content: Projectile Motion at an Angle Terms- Review Criss Cross Puzzle

Projectile Motion at an Angle


1. It is affected by gravity throughout the projectile motion

4. R=square root of A^2+B^2


1. This has magnitude and direction

2. These can be derived from the resultant vector and produce x and y values

3. this determines the sign of the x and y component vectors

5. the measure of angle in degrees counterclockwise from the x axis(right)

Friday, November 6, 2009

Content + Application: Eric's Physics Projectile Motion Vs. Roger Federer Video

You are about to enjoy my video over projectile motion at an angle including real tennis court measurements, correct and complete equations, and class humor!
By creating this video I now know inside and out!  Ask me if you have any questions please!  It is not simple so please ask before you waste your time!

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Content: Projectile Motion at an Angle Content


Honor Bound

November 5, 2009


Physics Projectile Motion at an Angle

The initial approach to a projectile motion problem at an angle is to break down the initial resultant vector into its X and Y components (Vox and Voy). You can do this by using the equations Vox = V * cos (), and Voy= V * sin (), where  is the angle above the horizon. After the projectile is launched, it is basically a free falling object with respect to the vertical with an acceleration of -9.8 m/s**2, due to gravity. The X component of velocity (Vox) remains constant throughout the projectile’s trajectory. There are two special points in time during a projectile’s trajectory. The first is when the projectile reaches its maximum height. At this point in time the Y component of velocity is 0 m/s. The second important time is when the projectile is at the same altitude as when it was launched. At this point the Y component of velocity has the same magnitude, but the opposite direction (the sign is opposite). If the altitude of the projectile is above the launch point, then vertical displacement is a positive number. Likewise, if the projectile falls below the altitude of the launch point, then the vertical displacement is negative. This becomes important in problems such as a projectile being shot off of a table or a cliff where the point of impact is at a different altitude than the launch point. The range of the projectile can then be found by finding the time at which the object strikes the ground. Examining the vertical motion in a situation does this. The range is then calculated by using Vox equal to the horizontal displacement times time. These equations ignore compounding factors such as air resistance and friction.  By firing a projectile at an angle of 45 degrees you can botain the greatest range.

Thursday, November 5, 2009

Introduction: Physics Projectile Motion at an Angle!

Thursday, October 29, 2009


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