Unit One Overview

What have we learned?

Inertia

In this unit I learned about the inertia of objects, but in order to grasp a clearer understanding of what it is you have to know Newton’s first and second law of motion

1^st law: An object at rest tends to stay at rest unless acted upon by and outside force.

2^nd law: An object in motion tends to stay in motion unless acted upon by an outside force.

Basically here we see the two natural states an object can be in until acted upon by an outside force. Inertia is the property of a object, not to be mistaken with a force. Mass is even a measure of inertia, objects with more mass have more inertia, meaning that they require more force to change it’s state of motion. If you look farther down on my blog I have posted a video that represents inertia well, I even put a description.

Equilibrium and Newton’s

Another two related topics that we learned are the concepts of equilibrium and net force. Equilibrium occurs anytime the net force (total forces) on an object add up to zero newton’s, this can only be accomplished when an object is moving at a constant velocity, and when it is not moving. A force is a push or a pull, therefore the net force is how hard someone/something is pushing or pulling on an object. A force in measured in Newton (N). Since weight is a force, we can tell how many newton’s are acting upon an object that has mass.  

Speed and Velocity

The first step in understanding speed is that it is the measure of distance someone/something has traveled over an amount of time (distance over time). For example when Usain Bolt runs the 200-meter dash, he is covering the same amount of distance (meters) as every other runner but in less time (seconds). Speed can be measured in various units, as long as there is a distance being covered in some given time, but the most common measurement is meters per second. The concepts of speed and velocity are very similar for both of them are measured in meters per second, and show how much distance someone is covering in a given amount of time. The significant distinction between the two is that velocity requires a specific direction; moreover, when discussing velocity we use vectors to describe the magnitude of speed and direction of an object. One example that helped me distinguish between the two was a racecar moving at a constant speed on a racecar track. Here the car is changing direction every turn it makes, but with velocity you can’t change direction without changing it’s velocity; therefore, the car is only moving at a constant speed (not constant velocity). Another way to change velocity other than changing direction is by speeding up or slowing down.

Acceleration  

Another main topic that we covered in this unit was acceleration. Acceleration is the change in velocity over the time (a=∆V/t). The symbol “∆” means change; we also learned that in this unit. The units for acceleration is meters per second squared (m/s^2) this can also be read as meters per second, per second, for it is the amount of change in velocity per second. What made the concept of acceleration clearer for me was the example of a ball rolling down 3 different shaped ramps.

In ramp A the ball moves with increasing acceleration, for the rate of velocity is increasing every second. In ramp B the ball moves with constant acceleration, which means that the speed of the ball increases at a constant rate. In ramp C the ball moves with decreasing acceleration, and although the ball is increasing in speed it’s acceleration is decreasing because the ramp is less steep in the middle.  The acceleration is decreasing slowly as speed increases.

Common equations that are asked that relate to acceleration are:

• How fast is “it” traveling?

The key word here is “fast” because instantly we know that the question relates to velocity. The equation used to solve this question is: velocity equal to acceleration multiplied by time (v=at)

• How far did “it” go?

Here we know that the question is asking for a distance, and the equation we use to solve this is distance is equal to one half the acceleration multiplied by the time squared (d=1/2at^2)

What I found most difficult in this lesson was distinguishing speed and velocity, and how you can have constant speed but not constant velocity. What really helped me in understanding this was the podcast project that I did with my group (video is at the bottom of this post). After much discussion and filming about velocity and change in velocity I became somewhat an expert on the definition of velocity. My first approach to homework assignments is to get it done quickly but at the same time diligently. The workload this year has definitely been greater, so I don’t get to spend as much time as I would like processing my physics work. The lack of time I get outside of class to work on homework only makes me want to pay closer attention in class so that I take less time trying to understand the homework. This strategy has worked well so far, I find that doing my homework after class or after listening to one of my teachers podcasts that it is rather easy to work through problems. My self-confidence in physics grows everyday as we learn new topics, even when posting on this blog I realize that it organizes my thoughts about physics well. Another thing that aids to this confidence is group work, for when my group came together to work on a podcast we were able to discuss the topic accurately to one another and when one of us had a question the rest of the group was able to answer it. A technic that I found helpful with all of my homework and quiz problems is patience. Taking the time to thoroughly read the question and check your answers can only increase the likelihood of you getting the question right.      

            My goal for the next unit is to spend more time studying for quizzes. This unit I wasn’t able to spend as much time as I would of liked on studying for my physics quizzes, so hopefully I will be able to make this happen by coming into conference period and asking clarifying questions that I may have.

• Here is a podcast about velocity that my group made in class, hope you like it!

Comparing Constant Velocity to Constant Acceleration

The purpose of this lab was to compare constant velocity to constant acceleration. Constant velocity means that an object is not changing in speed or direction, the two cases in which this occurs is when the object is not in motion and when it is moving but not accelerating. Constant acceleration occurs when an object is changing speed at a constant rate.

The lab we did in class involved rolling a metal ball across a table at a constant velocity and marking down on the table every .5-second made on the metronome (steady pulse). As a group we then measured the distance between each mark to calculate the constant velocity in which the ball moved at. We knew that the ball was traveling at a constant velocity because it traveled 19 cm per .5 second. In part two we tracked the movement of a marble moving at constant acceleration on an inclined surface. The marks grew increasingly apart as time went on due to the fact that the ball was gaining speed. As a group we measured the distance between the starting marks and the marks made afterwards (.5 seconds apart) to serve as the x and y axis on our graph.

The formula used for constant velocity is (v=d/t) which is the distance divided by time. For all graphs made to show constant velocity the distance between points will always be equidistant. The formula for constant acceleration is d=(1/2)at^2 which is the distance equal to half of the acceleration multiplied by the time squared. On our graph showing constant acceleration there was a curved line connecting to the dots.

This graph shows constant velocity. The graph we made in our
lab for constant velocity looked similar to this

This graph shows constant acceleration. The graph we made in our
lab for constant acceleration looked similar to this

Velocity and Acceleration

http://www.physicsclassroom.com/mmedia/kinema/avd.cfm

This website helped me grasp a clearer understanding between the concepts of velocity and acceleration. The website states how velocity is the speed and direction of an object, while acceleration is the change in velocity over time.
Example of acceleration: Car moving from 0-60 mph
Example of velocity: Car going west at 60 mph

Hovercraft

Today in class we rode hovercrafts across the gym floor. If you have never been given the opportunity to ride one it is almost like floating on a cloud. In comparison to other moving objects such as a sled or a skateboard, the hovercraft moves at a constant speed, this is particularly due to the fact that it has zero friction. Once the individual pushing the hovercraft lets go, it continues to move at that same speed until someone stops it. An interesting fact that I learned while pushing and stoping the hovercraft was that some things resist changes in its state of motion, this is a result of its mass. The people with more mass have more inertia; therefore, the hovercraft was harder to start and stop. Objects that contain more mass have a greater tendency to resist change in motion. Anther thing I learned was that the hovercraft only has a net force of zero when it is stopped and when it is moving at a constant velocity. While the hovercraft was stopped it had no forces acting on in to move. Likewise, when the hovercraft was moving at a constant velocity there was an equal amount of newtons on both sides of the hovercraft causing it to move and not slow down. For any object with a net force of zero it is also in a state of equilibrium, this is because it's acceleration is 0 and there is an equal balance of newtons pushing on the object on both sides. Based on this lab, acceleration depended on the person putting force on the hovercraft in order to make it move.

Inertia fail

Inertia: An object in motion tends to stays in motion. An object at rest tends to stay at rest.

In this video inertia is represented when the plates that are at rest stay at rest even when the cloth is pulled from underneath them. The dishes don't speed up because of their inertia, but if the table cloth pulls the dishes longer, then they will begin to speed up and move along with it.

Intro.

• This year I hope to develop a better understanding on how physics can relate to our everyday lives. In class I also expect to learn more about inertia and how it occurs. Also I would like to grasp a deeper understanding of Newtons theory of relativity.
• Physics is an important subject to learn about, because it gives an explanation of why things are the way they are. The role of physics in technological advancements is crucial, for without it we wouldn't have the inventions of cars or computers. Another basic reason why physics is important is because it is the reason for everyday happenings.
• Questions that I have about physics; why do air bags keep you safe in a car? How do credit card machines read your information when you swipe your card? how do different musical notes blend together to make harmony?
• My goals this year for physics include; turning in all assignments on time, plan to make time in advance to study for tests, and reach out to my fellow classmates for help or to collaborate on studying for tests.