Well, it's the last unit before our semester ends. It's crazy to think of all we've learned. WE started out this unit by studying Newton's 3rd Law, which basically says for every action there will be an equal and opposite reaction. This is when the action-reaction pairs came into play. To give an example of this, let's say that I push up against the wall. Well, the wall also pushes against me. Another example is if a baseball bat hits the ball, then the ball will hit the baseball. One of the concepts we used to demonstrate this law is a horse and buggy. The horse pulls the buggy so therefore the buggy pulls the horse. However, there are other action-reaction pairs that go along with this. The horse pushes the ground backwards, so therefore the ground will push the horse forward. The same thing happens with the buggy; the buggy pushes the ground backward and the ground pushes the buggy forward. The ultimate reason that the horse moves the buggy is because it pushes against the ground with a greater force.
The next thing we learned about is vectors. Now, this is a little hard to explain without pictures, but I will do my best. Basically, a vector causes an object to move in a certain direction. For example, if a boat is faced straight ahead, it will end up going in a diagonal downward because of the current. We represent vectors with parallel lines. Where these lines intersect shows what direction something will be going in. We used vectors to explain why a sled will go down a hill. Vectors also helped explain how to make a rope with a weight on it completely straight. We can figure out the various tensions in the ropes, by making a parallel line that corresponds with a side of the rope. This will also help explain which side of a rope has more tension than another.
Universal Gravitation Force gave us the ability to measure forces between any two objects anywhere. We know that anything with mass attracts all other things with mass. We also know that force depends on the mass of an object, making this two proportional to each other. The distance between between objects will be indirectly proportional to the force, making it 1/d. In this instance, we use an inverse square law, which means that the distance will be squared. This helps us set up our equation. Based on the above information, our equation will be F=G(m1m2/dd). G represents the gravitational force on an object. This number will not be the same because the distances between the objects will always vary. This number will be given to you.
The Universal Gravitation Force helped set up our next lesson, tides. We know that the moon is closer to the Earth than the sun is. As a result, there is a very large force between the sun and the Earth. We know that there are two different sides of the Earth; For our purposes, lets call them side A and side B. The force between the two sides of the Earth and the moon will be different. When side A is the closest to the moon, there will be a greater force, because the distance is smaller. The opposite happens when side B is further away from the moon. There will be a larger distance between this side and the moon, which will therefore cause a smaller force. This is the ultimate cause of tides. The different forces cause an oval shape to form around the Earth called a tidal bulge, which represents the high and low tides. Each high and low tide will happen twice a day, totaling four times a day. Between a high tide and a low tide or vice versa, there will be a six hour difference. Accordingly, between a high tide and a high tide or a low tide and a low tide, there will be a twelve hour difference. High and low tides will not happen at the same time each day, because the moon is constantly revolving around the Earth. It takes the moon approximately twenty-seven days to make a full circle. We have two different phases of tides called spring tides and neap tides. During spring tides, the moon will either be full or in the new moon stage. The tides go to the extremes as the high tides will be much higher and the low tides will be much lower. Hurricane Sandy hit during a spring tide, which meant there was much more damage because the tide was so high. In neap tides, there will be half a moon. During this time, the tides won't be as high or low as usual.
We spent the next half of the unit focusing on momentum, changes in momentum, and the impulse. Momentum is defined as inertia in motion. The equation to represent this is mass times velocity. However, when the direction is not important, we use mass times speed. It is possible for momentum's to equal zero; this will mean that this object is in a state of equilibrium. When anything with mass moves, it has momentum. Moving on, impulse is best defined as force multiplied by a time interval. When a change in momentum occurs, this will be a change in the mass times velocity. If the mass stays the same, then the velocity will change and acceleration will occur; this is most common that will happen. The more force, and velocity, then the greater the momentum. We know that change in momentum will be the final momentum subtracted from the initial momentum. Based on the equations, we know that impulse will be equal to the change in momentum. A question we answered during this section is, how do airbags keep us safe? Well we know that the momentum will be the same no matter the collision, and the change in momentum will be the same, so the impulses will be the same. Airbags increase the time impulse occurs, which means the force will be less. A smaller force will lead to less injury. We learned that bouncing can negatively effect this. When things bounce, the impulse will be greater, which will cause a greater force, and ultimately a greater impact.
The last thing we learned about is the conservation of momentum. We learned through a lab, that if two cars collide, the initial momentum will be the same as the final momentum. If we add the initial momentum's together, we should get the answer to be zero because one of the momentum's will be negative since it will be going in the opposite direction. This is the law of the conservation of momentum. We had several equations for this unit. When two objects collide head on, then we will use, momentum before=momentum after. When two objects collide and stick together we will say that the momentum before=the masses added together and the Vab (which represents the velocity of A and B stuck together.)If two objects collide, one in moving in a vertical direction and one in a horizontal direction, we will use vectors to find the new velocity. We draw the parallelogram and will find the hypotenuse of this box by using the Pythagorean Theorem.
This unit has presented various different challenges. Certain concepts have been hard to understand at times, such as vectors. It took me a few times to correctly draw a picture to show how a box slides down a ramp. I didn't really understand what all the various lines represented. The pictures seemed to cluttered and too confusing. Vectors didn't come easily at first, but I spent time each day studying them, and redrawing pictures. Once I had drawn my tenth vector, things seemed to click in my brain. I understood the f-weight, and the f-support. Things began to seem a lot simpler. It also helped taking quizzes on these concepts, as I got to practice my drawings even more.
I definitely feel that as Physic's continues, I have more confidence and seem to understand more. My brain has been rewired to comprehend the world of Physics. Because of this new-found confidence, it is much easier to solve problems with patience and accuracy. Problems that originally would have left me awe-struck now seem much easier, and make much more sense. Also, I really think the voice thread and pictures for each unit help think of Physics in a more creative way. The podcast also challenges me to think in creative ways to present an interesting concept to the class, which will help them better understand what we learned.
My goal for the semester exam is to go in with confidence, and study ahead of time. It really helps to pace yourself considering there are four other exams to worry about. My plan is to have a concept to study each day. Also, I need to ask questions when I have them.
I feel like this unit has been the most relatable to real life. We learned about the tides and can now answer the question if you made a sandcastle at night during low tide, would the sandcastle be there in the morning? We also learned about the universal gravitational force. Out of all units, this has been the most intriguing.
