Sunday, December 6, 2009

Newton's First Law

I learned many things from our studies of Newton's first law like FBDs, translational equilibrium, inertia, how to find the sum of the forces, or find the value of one specific force. I had heard of Newton's First Law before studying , but I hadn't really known what it was. The law basically states that objects at rest stay at rest and objects in motion stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. This goes along with the idea of inertia and how objects resist change in motion. An object has forces acting upon it keeping it in motion, slowing it down, or keeping it from moving. To show all the forces acting on the object we learned to make FBDs or Free Body Diagram. These helped me get a clear visual of the forces acting on an object and would later help me when I was finding the sum of the forces or the value of a force. To find the sum or value of forces, you have to know about translational equilibrium or when the vector sum of the forces acting upon an object are equal to zero. To find the sum or value you would add or subtract(depending of the axis) the force and set them equal to zero. We would apply SOH CAH TOA to adding or subtracting the forces. We would use a separate equation for each axis.
The most difficult thing for me in this unit was finding the angle, when one was not given. In some of the problems especially the ones where the axes had to be tilted I had trouble finding the correct angle. I learned to add horizontal and vertical lines to the drawing and  to make a right triangle with each of the angles and find the sum of the last angle. I then could apply the angle found the the correct equation and solve. I have learned many problem solving skills from this unit the main one for me was patience. While doing the homework and classwork I learned that you can't just go through the problems fast and carelessly. I had to start from the beginning and draw the correct FBD with all the right forces then figure out what I was trying to solve for and if needed find the correct angle. Then make an equation that would solve the problem. I also had to remember all of the trigonometry that I had learned in the first trimester; going back to those pages to look at the things I had forgotten like when to use SIN and When to use COS. Also to solve an equation that I had to make. I had to get used to the idea that I would not just plug numbers into an equation and calculate that I had to make one myself and then solve. This unit also had me go back and carefully check my work because if I started off wrong from the beginning it would mess my whole problem up.

There are many ways Newton's First Law is used in our everyday world. For example pulling my heavy backpack across the floor, I'm applying a force. Or when a car is braking the friction between the ground and the tires. Or when they are building bridges and they have to figure out at what angles and the the weight the bridge can be at to have it be safe. Or when you are hanging object on your Christmas tree, you have to have a strong branch to support the heavier ornaments. Also when you roll a ball it doesn't stop until friction or it hits something.

Thursday, November 12, 2009

Content-Acceleration

Dear Grandma,
I got your letter and I would love to answer your questions about acceleration, to help you better understand your knowledge of physics.
Well the direct definition of acceleration is the the change of velocity over a period of time.
Q1) Is acceleration just when an object is speeding up?
No. Acceleration is just the change in velocity, whether that object is speeding up or slowing down it does not matter.
Q2) When does acceleration happen?
Well as stated above it happens when and objects velocity changes. Acceleration also happens when the object changes direction. For example if a car is turning. Acceleration is a vector quanity, so that means it invloves both magnitude and direction. The speed of the car stays the same, but the direction the object is moving changes.
Q3) What is free fall and how does it relate to acceleration?
Gravity is a force and when an object is in free fall and air resitence can be neglected, the acceleration due to gravity is 9.8m/s^2
Q4) Why is acceleration a vector quantity?
Vectors include both magnitude and direction. Acceleration depends on what direction the object is traveling in(either positive and negative) and the numerical value.
I hope I have answered all of your physics questions clearly, please write me if you have any more.

With Love,
 Emily

Monday, November 9, 2009

Content-Acceleration

Acceleration Wordle:

Friday, November 6, 2009

Content-Acceleration

My Acceleration Voki!