Unit 2 Summary

Unit 2 Summary:

The second unit was about Newton's Second Law:

Newton's Second Law is:
 acceleration is directly proportional to force and inversely proportional to mass.
or:
a=F(1/m)

In the Newton's Second Law lab, we set out to prove this. 
We did so by changing mass and Force to see how it would affect acceleration.

In the first experiment:
-we added mass and found that when we added mass and measured the acceleration, the acceleration decreased. 
-Then we graphed the data and compared the equation of the line to Newton's Second Law. 

y=mx+b
a=F(1/m)

The slope of the line is always the factor we kept constant during the experiment. 
in this case, it was force(we kept force constant by keeping the weight of the hanger constant).

When we compared the slope(theoretical force), to the actual force we measured(the wight of the hanger), we found that they were often within 10 percent of each other, depending on which group you asked. If it was within 10 percent, we can say that it suggests Newton's Second Law is true.

In the second expierement, we repeated the same procedure, but kept mass constant and increased force. We did so by transferring the mass from the cart to the hanger. We found that when we increaced the force, the acceleration also increased.

Then we learned about Free Fall, that is moving without air resistance. 

In free fall, the only force acting on the object is gravity. The force of gravity in free fall is 10m/s^2. 
-When a ball falls, the speed increases by 10 m/s every second. 

-When a ball is thrown up, it decreases every second by 10m/s. 
-at the top of it's path, the acceleration is 0 and it is at equilibrium. 
-When it falls back down, It increases every second again. 
*when calculation for a ball that has been thrown up and has come back down, you can only use the formulas if you measure the path it took starting at 0m/s.

For instance, to find the total time in the air, you must use d=1/2at^2 only for the path from equilibrium(at the top) to the ground. Then you can double the time to get the answer. 

Throwing things up at an angle:

When you throw things up at an angle, you must use the vector as the hypotenuse of a triangle with the other sides being vertical velocity and horizontal velocity. You treat the vertical velocity the same as you would throwing straight up as it increases by 10m/s when falling and decreases by 10m/s when rising each second. The hypotenuse of the triangle is used to determine the actual velocity at each second. 
*the angle may help you determine of the triangle is a special triangle

Projectile Motion:

When measuring projectile motion, you must take into account the vertical and horizontal properties. You must use different equations for each one: 

vertical:
d=1/2at^2
v=at

horizontal:
v=d/t
d=vt

Use each of these to find whatever part of the problem you are asked for, but make sure you are using the right equation. Hight determines time so the time will be the same for both of them.
To find the actual velocity at any given second, you create a triangle with the speed on each side, both horizontal and vertical, and the hypotenuse represents the actual velocity.

Falling Through the Air(Falling with Air resistance):
When falling through the air, you can measure the net force of the object with this equation:

Fnet=Fweight- Fair. 
Two things can affect the force of air resistance
-speed
-surface area

When you first jump off, your speed begins to increase, this increases the force of air resistance and you acceleration starts to decrease, as does your Fnet(see equation with increasing Fair). This does not mean velocity starts to decrease as well, in fact it continues increasing. When the object reaches terminal velocity, it is at equilibrium.

But, if the object were say a person skydiving, and that person reached equilibrium and then opened the parachute, the acceleration and Force would both decrease because the Fair increases because the surface area increased. Then the skydiver will reach a second terminal velocity, however, it is going at a slower speed than the first.
*The force of air resistance is the same for both terminal velocities.

Resource

http://www.physicsclassroom.com/mmedia/newtlaws/sd.cfm

This source helps explain the Physics of Skydiving.
This video is also helpful for understanding projectile motion:

https://www.khanacademy.org/science/physics/one-dimensional-motion/old-projectile-motion/v/projectile-motion-part-1

Unit 1 Reflection

Unit 1 Reflection

1.) This unit I was a combination of Procedural learner and Committed learner. I was procedural because i had to learn a lot of concepts really fast and I didn't focus a lot on the why or how for those concepts. But for the last part, the equations part, I asked a lot of questions and made sure I understood more than I needed to.

2.)I had a lot of difficulty grasping the Speed vs. Velocity concept. It makes sense to me on paper that velocity includes direction, but conceptually it was hard for me to understand what effect direction has. I overcame the challenge by asking questions.

3.)The way I studied throughout this unit was by making sure I understood how to do the questions of the homework, and for questions I missed on the quiz, I tried to figure out why(ie. I didn't study that, or I didn't understand etc.). I think in the future, I should continue to use that strategy. Also in the future I should start the blog post earlier as review.

4.)I took the opportunity in class to really focus on how to do the homework problems and other problems when we went over them in class which was helpful. Out of class I watched the videos on the website which explained a lot of concepts.

5.)I predict I got a high B. I think I was mostly able to demonstrate my understanding of the concepts, however, there were a few concepts I think I understood and had trouble applying. For future tests I want to make sure that I pay attention to the problems we do in class because they will help me learn how to apply the concepts.

6.) I learned from your feedback mostly in class when I thought a concept was one way it helped when you explained why it isn't that way. The feedback I hope for in the next unit is the same kind of explanatory help.

7.) I got better at working with other people and at  doing work when there isn't a definite headline, I just need to know the material. Hopefully next unit I will get better at something else, but I do not know what it is. Usually when I improve I don't know I need to until it presents itself as a problem.

8.) I would give myself A 8/10 for effort because if I were to have put as much as I should have retrospectively I should have come in and asked for sample problems on the first couple of concepts I missed because It would have helped on the test.

9.) you should know that I think physics is more interesting than chemistry so far.

What Did We Learn in Unit 1

What Did We Learn in Unit 1? 

Physics starts with forces and how they act on things.

The first concept adresses Newton's first law which is that: an object at rest will stay at rest and an object in motion will stay in motion unless acted upon by an outside force. Inertia describes an objects tendency to resist a change in rest or motion. Mass is a measure of Inertia. it may seem as though Inertia can be a measure of Mass because we are familiar with Mass first, however, it is the other way around.  An example of Inertia is suppose you have a refrigerator and a soccer ball. You try to move them both 10 meters, but it is very hard to move the refrigerator, and easy to move the soccer ball. The Inertia of the refrigerator is greater because it has more resistance to change it's state at rest.

Net Force and Equilibrium:

A force is either a push or a pull that acts on an object. The force is measured in Newtons(N). The Net Force is the sum of all of the forces acting on an object. If an object is at equilibrium, that means the Net force is zero. An object can be at equilibrium when it is at constant velocity or at rest. 

Example Question:

If I push on a box from one side with a force of 100N, and Caroline pushes on the other side with a force of 75N, what is the Net Force? Is the box at equilibrium?

Answer: 25N, no

Velocity and Speed:

Speed is a measurement of how fast an object is going. You measure speed by covering and objects distance in a period of time. An easily understood example of this is how we measure the speed of out cars- in Miles per Hour. As in, how many miles(distance) is the car covering in a period of time (miles).

Velocity is more specific because it refers not only to the distance in time, but also to the direction. An object can maintain speed, but change velocity by changing it's direction. This is because it takes an acting force to change direction. An example to think about is riding a bike around a baseball field. If you follow the perimeter, you can keep the same speed, but since your direction is constantly changing, your velocity is not constant.

There are two ways to change velocity: speed up/slow down, or change direction

The direction portion of velocity is shown using vectors, which are basically arrows. They convey both the magnitude, or the speed of the velocity and the direction.


Acceleration:

Acceleration is a change in velocity over a period of time. Speeding up is acceleration, but slowing down is also acceleration but in the opposite direction. Acceleration is measured in meters per second squared rather than just meters per second. If an object is falling straight down, the acceleration is always 10m/s squared.

Constant Acceleration and Velocity: Constant Velocity is when for any given time the speed and direction are the same. Constant Acceleration is when an object is speeding up or slowing down the same amount each second. Constant Velocity and Constant Acceleration are mutually exclusive. 

 Calculations:

https://www.youtube.com/watch?v=O2yG-5yiuhQ&feature=youtu.be


To calculate Acceleration you will need three formulas:

The equation for acceleration: acceleration = change in V/time

Distance:      d=1/2 a t^2
Speed(how fast):  v=at

Formulas for Velocity:

v = d/t
d = vt

Learn Them!