TOP TEN FORMULAS AND EQUATIONS OF PHYSICS!

Top Ten Laws and Formulas of Physics

1.      Newton’s First Law

Newton’s first Law of Inertia states that an object in motion will stay in motion and an object at rest will stay at rest unless acted on by a net force. This concept is important because it is the basis for most physics concepts. An example of Newton’s first law would is used when you are in a car, and toss a coin up in the air. The coin will land in your hand and not behind you because the car, coin, and you are in motion and will continue to stay in motion until a net force acts upon you!

2.      Speed=distance/time

This concept is important to physics because it is the basis of many of the physics equations that we have learned throughout the year. Through this equation we are able to learn that Acceleration is equal to change in speed/time. With these equations, we were able to solve many physics problems. For example, if a car has gone 4 meters in 2 seconds, you can plug this information into the equation (speed=4/2) to find out that the car is going 2 meters a second.

3.      Distance traveled=1/2(acceleration x time²)

This equation, d=1/2 gt² was very important to learning about falling objects. Using the equations I had learned beforehand, I was now able to solve problems that asked me to find the distance that the falling ball had traveled. Know that I knew the basic physics equations, along with v=gt or velocity is equal to acceleration times time, I was able to solve most distance and time problems!

4.      Newton’s second law

      This law states that the acceleration of an object is directly proportional to the net force acting upon the object, and is in the direction of the net force which is inversely proportion to the mass of the object, or better known as Acceleration is proportional to net force/mass. This law was useful, because it was then that we began to learn about free fall. Using this equation I learned that in free fall, weight will be equal to resistance, so all objects no matter size of weight will fall at the same rate! While learning about this subject, we learned by example that a feather and a penny will fall at the same rate in free fall, because force of the object will be equal to the mass, so the acceleration will always be equal in free fall!

5.      Newton’s Third Law

Whenever one object exerts a force on another object the second object will exert an equal and opposite force on the first, or in a condensed version, every action has an equal and opposite reaction. This law is extremely important to physics because it is something that you don’t think about very often, but is needed for humans to live. Examples of newton’s third law would be if I was walking, I would push the floor backwards, and the floor would push me forwards, allowing me to walk, but the force would be equal and opposite. That is why, if I attempted to throw a piece of paper, it would not go very far because I can only exert a much force on the paper, as it can on me, and since it does not have very much mass, I cannot throw it very far!

6.      Work=fd Power=work/time

The formulas for work and power were very important to our class this year. While learning that work is equal to force times distance, we also learned that a Watt is how quickly work is done. This would later be beneficial to many of the equations that we would solve. By learning about power we could later apply this to how to power a light bulb through the equation I=V/R, but we would have not been able to find that out if it was not for the power and work equations. This concept showed me that in order to understand physics; you must understand all parts of the science.

7.      The change in Kinetic Energy is equal 1/2mv² and work

This formula is very important to our class because the change in KE is also equal to work. This equation allowed us to learn the answers for many questions such as how airbags keep us safe from getting hurt, to why there is padded grounding in gymnasiums. I learned that airbags keep us safe, because when you are in a car crash, you go from moving to not moving very quickly , and momentum is P=mv. The change in momentum is the same regardless of hitting the dashboard or the airbag. Because the change in momentum is constant, the J or impulse is constant also, so the airbag will increase the distance so that the force will be reduced in the equation J=f x the change in time, so the airbag will spread the force out over a longer period of time, making your chances of being hurt go down.

8.      Centripetal Force and Centrifugal Motion

While learning about these concepts, I learned that centripetal force is a center-directed force that causes an object to follow a curved path, while centrifugal force is the apparent outward force on a rotating body. I was able to connect these physics concepts by finding out the answer to why we move while in a turning car. I learned that centrifugal force doesn’t actually push you into the car door, but the real reason you hit the side of the car while turning is because NO force is acting upon you. Newton’s first law states that an object in motion will stay in motion unless a net force acts upon it, so in this case, since the car was moving in one direction and then changed, your body will continue to want to go in that direction but the car door will act as the net force that hits me and forced me to move towards the center of the circle that the car was making during its turn. Because of newton’s third law, I will push the door in, and the door will push me out, and so I will stay safely in the car.

9.      I=V/R

This formula states that current is equal to voltage divided by resistance. In order for current to flow there must be an electric potential difference. This is why it can be dangerous to plug an American appliance in into a European socket. European sockets have a much higher voltage, meaning there is a higher electric potential difference so there will be a lot of current running through the appliance. Our devices are not meant to have such a high amount of current running through them, so it may start a fire but because the European appliance expects a higher current, a lower current coming from an American appliance will not hurt the appliance or start an electrical fire.

10.   Opposite charges attract and like charges repel

We learned this concept while dealing with magnets. I learned that the charge of the

magnets always flows from south to north, and when opposite charges are near each other, they will be attracted, but if they are like charges, they will repel from each other. I learned that the reason your hair becomes frizzy after brushing it is because when you brush it, the brush will steal electrons from your hair, making your hair have a positive charge. Then the comb will become negative because of the stolen electron’s charge. We now know that like charges repel, and so your hair will stand up to get away from the other strands of hair.

Centrifugal Motion; The force that isn't actually a force!

Centrifugal Swingin' 

Category: Natural photo

              This picture demonstrates the physics that is incorporated when one swings on a swing. As you swing, your body will move with the swing, as the chains keep your body and the swing moving in a circular motion. Once you let go of the swing, there will no longer be a net force moving you in a circular motion, which was once the chains, and so your body will travel in a path tangential to the circle. On the other hand, as you can see, the swing will continue to move in the direction that it was before because no net force will act upon it. This notion is from Newton’s first law which states that an object in motion will stay in motion and an object at rest will stay at rest unless a net force acts upon it. This rule applies to both the swing and your body. In this case, the body will continue to move in the direction that is tangential to the circle until a net force acts upon it, which in this case will be gravity.

Magnets and more!

What I learnedThis section was a lot of fun! We started off by learning about magnets and electromagnets, and learned that a current carrying wire experiences a force when it is in a magnetic field. We also learned that change is very important to this section. In fact we learned that when a magnet moves through a wire, it changes the magnetic field thus inducing voltage and causing current. This is because in all objects, there are domains of atoms that spin, and when the domains are moving in the same direction, it creates a magnetic field, making the object a magnet. This shows that you can create and destroy magnets pretty easily by disrupting the direction of the domains by striking the magnetic object to align the domains. Going back, we started this section by learning about magnets. I learned that each magnet has a north and south pole, and that force always flows from south to north, so opposites will attract while like poles repel.  While still learning how magnetic fields work, we started the mini motor project! In this project we created our own mini motor, and learned how motors in general work. I learned that a motor works because a current carrying wire feels a for in a magnetic field. And in this case, the battery supplied energy for the current and the loop of wire and paperclips then carried the current to complete the circuit. The magnet supplied the magnetic field and so the wire loop felt a torue in the magnetic field when current ran through the wire when the side of the loop that was scraped of was vertical to the battery and magnet, thus the loop experienced a torque and turned, creating a mini motor! At this point we also learned how stoplights detect cars! In the ground there is a coil of wire in the pavement. So, when your car, which acts as a magnet runs over it the magnetic field, it will then change the magnetic field and induce voltage causing current. The flow of current then acts a signal for the light to change!  

 




 Connections to the real world…This section, I was able to connect many things to the everyday world! That’s what physics is about, isn’t it? One major thing that I learned was how security metal detectors work at the airport. I learned that they work, because throughout them, there is a coil of wire that carries a current in its own magnetic field, so when someone walks through the detector and is carrying metal, they change the magnetic field which induces voltage causing current to make a beeping noise to alert the TSA workers. Another thing that we actually took a field trip on that is a connection to the real world is how stoplights work, and it is actually very similar to how the metal detectors at the airport work. There are coils in the ground and your car acts as a magnet and changes the magnetic field in the coils, which therefore induces voltage and causes current acting as a signal for the light to change.

 


Problem solving skills….This section has not dealt with problem solving skills very much, but when working with transformers I was able to put my skills to work. By using the equations P=IV which means that for transformers the current of the primary times the voltage of the primary will equal the current of the secondary times the voltage of the secondary, so with this I am able to use the equation that states that the amount of voltage of the primary coil over the amount of turns in the primary coil is equal to the amount of voltage of the secondary of the turns of the secondary, so reverting back to Newton’s 3^rd law, every action has an equal and opposite reaction.

What I found difficult…This section, a concept that I felt was hard for me to grasp was how transformers work. I learned that transformers have coils of wire next to each other, where the primary has a lot of turns and the secondary has less turns, and the amount of turns is proportional to the voltage, so because there are less turns normally in the second than the primary, the voltage will be decreased, it that is your use for the transformer. The current running from the wall is alternative current, or ac which means that the voltage is constantly changing directions, and thereby changing the magnetic field and inducing voltage, creating current. The secondary’s magnetic field will change because of the change in the first’s magnetic field, and allow the transformer to work . It took some time for me to understand transformers, but after going over them with Ms. Lawrence, the subject was cleared up! Then, Going along with motors, it was difficult to see the differences between a generator and a motor. I then learned that a generators input was mechanical, while its output was electrical and made to work when the change in the magnetic field induced a voltage and caused a current, allowing the generator to work, but that a motors input was electrical, and it’s output was mechanical, and worked when the current carrying wire felt a force in a magnetic field. They really are two different things!