Top 10 most useful concepts of Physics!

The Top ten most useful concepts of physics!
 1. The first most useful concept of physics would be Newton’s first law. Newton’s first law states that an object in motion will stay in motion or an object at rest will stay at rest unless a force causes it to change. This is also known as the law of inertia. This concept is important regarding car safety. Cars are now designed based on this law in the case of an accident. Manufactures look at the law of inertia and design airbags, seatbelts, and headrests to protect us from getting injured. If a car is at rest at a stoplight, everything in the car is at rest as well. If a car were to rear end it, the car would move forward, but everything in the car would want to stay where it is. For example, our heads, if there were no headrests that would force out heads into motion along with the car, our heads would snap off. Because of Newton’s first law, scientists know this and are able to prevent that. Newton’s first law is extremely useful in that it helps save lives by providing scientists the knowledge to prevent certain fatal injuries.

 2. Acceleration is an extremely useful concept of physics. In fact, racecar drivers to win races use acceleration. A racecar driver wins a race by driving a set distance in the shortest amount of time going the fastest highest velocity. The common person may think that a racecar driver wins a race just by driving fast, however, a racecar driver wins not just because of his speed, but because of how fast he is speeding up. This is the physics concept of acceleration. a. Acceleration = change in velocity / time. While racecar drivers measure their speed in miles per hour, in the world of physics, we measure speed in meters per second. In order for a racecar driver to win a race the physics concept of acceleration is vital to know.


 3. Another useful concept would be objects falling through air. The army uses this concept to drop supplies from airplanes to specific spots. Because of physics we can know how long and how far something will fall based on how high it is dropped from, what speed it is dropped at, and how great the air resistance is. This concept is extremely useful for the army because they are able to make precise drops of soldiers, supplies, and bombs with this knowledge.


 4. Centripetal Force! Lacrosse and roller coasters. Two very popular things in America are lacrosse and roller coasters. But what do these two things have in common? They both rely on the physical concept of centrifugal force. When an object is inside of something experiencing centripetal force, (any force directed toward a fixed center) that object is experiencing centrifugal force, an apparent outward force. It is helpful to know that Centrifugal means “center-fleeing”. For example, when you put an object in a can and spin that can around by a string, you will find that the object will remain in the can at all times. So what does this have to do with lacrosse and roller coasters? Well, lacrosse uses centrifugal force to keep the ball in the net pocket of the lacrosse stick. In order to do this, lacrosse plays move their stick in a back and forth motion called cradling. Cradling causes a centripetal force sensation causing the ball to experience centrifugal force and stay in the net of the lacrosse stick. Similarly, roller coasters rely on centrifugal force to keep people in their seats. For example, when a roller coaster goes around a loop, the people on the roller coaster experience a centrifugal force and are rooted in their seat throughout the loop. Centrifugal force is a key factor in having fun, it allows us to play sports as well as allows us to enjoy ourselves on roller coasters in amusement parks!

 5. Simple Machines, I.E. Ramps A ramp is a simple machine that makes things easier for us. Because of physics concepts, we know that the work we put into a ramp = the amount of work we get out of it (work = force X distance). The main principle that allows us to know this is the conservation of energy. The law of conservation of energy states that: Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes. Because we know that the work input and output are going to equal each other we know that the product of the input force and distance must equal the output force and distance. However, the input force does not need to equal the output force, just the product of the force along with the distance. (force X distance) input = (force X distance) output. Knowing this, a ramp allows us to use less force by working over a greater distance. (f X D) = (F X d)! For example: If you had a 40kg box and needed to lift it 3 ft, you could grab a 4ft long board and slide the box up it. Lifting the box would be 120 joules of work, and so would sliding it, however with the increased distance you would be required to exert less force in order to get it to the same point that lifting it would. A ramp is only one example of a simple machine designed to make out lives easier.


 6. One very useful concept of physics is rotational inertia. Rotational inertia is the property of an object to resist changes in its rotational state of motion. For example, a meter stick with a weight taped to the top is going to fall down slower then a meter stick without the weight. The stick with the weight was resisting the change more then the meter stick without the weight. So how is this useful? Baseball players appreciate this concept because with this knowledge, they know that it is easier to swing a shorter baseball bat then it is to swing a longer one. Being able to swing the bat faster allows players to hit the ball harder and overall improve their athletic performance. Similarly, rotational inertia is helpful for bikers as well. Bike wheels with a low rotational inertia are going to spin faster then opposed to larger ones. So a biker would want to get wheels with less mass on the circumference in order to bike faster and win. Along with bikers and baseball players, rotational inertia is important for runners. Runners with long legs are able to go slower with a larger stride, but runners with shorter legs are able to move them quicker but with smaller strides. The whole reason that runners bend their legs is because of rotational inertia. Imagine running with your legs straight! Physics concepts, as you can see, are very much so used in sports!


 7. One vital concept within physics is the knowledge of capacitors. Because of capacitors we have defibrillator and are able to save lives. When a person dies, their heart stops. Scientists have discovered that sending a charge through a stopped heart can sometimes restart it. In order to do this doctors use a machine called a defibrillator. A defibrillator basically builds up a large amount of charge in an incomplete circuit. When the two defibrillator paddles touch the body the circuit is completed and a charge is sent through the body, hopefully restarting their heart. This is the concept in a capacitor, which also causes the flash on cameras. In a camera there are two plates and there is a large amount of opposite charges built up on each plate. The circuit between the two plates is completed for a split second and a flash of light is released. Because of physics we are able to save lives and take good pictures!


 8. Current, -> light bulbs Because of the physics concept of current we now have the ability to light up light bulbs. Light bulbs are lit when current is flowing through its filament. Current only flows when there is an electric potential difference. For example, in a battery, one side may have a certain voltage, but in order for the current to flow, the other side must have a different voltage. In order for a current to flow up into a light bulb a circuit must be completed. This means that a conductor needs to make a full loop so that the current can flow through it. A conductor is something that allows current to flow through it. In the context of light bulbs there will always be a metal wire of some sort that conducts the current. Due to the physics concept of current we can light up light bulbs and have light inside of our homes!


 9. magnetism, compasses, used to find our way
 An extremely important use of physics would be compasses. With compasses we know which direction is north, south, east, and west. With this information we are able to find our way around with a good sense of direction and are able to locate things. A compass is just a free piece of metal that aligns with the Earth’s magnetic field. The earth has a magnetic field flowing through it from south to north. The flow comes out and around the earth back into the south side only to flow north again. Our geometric North is the magnetic south and vise versa. This is because on the surface of the earth we pick up the direction of the magnetic field as the south is flowing back up in order to re enter the earth and continue to flow to the north. Because of this magnetic concept, we are able to write maps, find our way when we are lost, and have a good sense of direction.

 10. Newton’s second law of motion, skydiving
 Skydiving is a sport where people fall out of a plane and float back to the ground by a parachute. Thanks to physics this entire sport is possible. Newton’s second law of motion states that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object. Mathematically this looks like: Acceleration ~ net force / mass. Skydivers are falling through air. For this there is a net force acting up on the person while gravity is still pulling them down. If you subtract these two quantities you come up with the net force. Take this number and divide it by the mass of the skydiver and you have his rate of acceleration. Because the diver is falling through air he will not exceed a certain speed, eventually he will reach terminal velocity. However, at some point the skydiver will open up his parachute. Doing this increases his surface area and therefore he increases the amount of air resistance on him. This is going to slow him down, eventually with his deployed parachute he will reach a terminal velocity at a speed that allows him to safely land on the ground.

Unit 7 Reflection!

This unit in physics we studied a lot of things relating to using motors, generators, and magnetism. We began with magnetism. We deducted that all magnetism is caused by current/moving charges. However, only charges moving in a given direction will cause something to be magnetic. This boils down to: Moving charges in a net direction will exhibit magnetic properties. This led us to once of the most important questions of Unit 7: Why does a paperclip stick to a magnet?

To start, we know that a magnet has domains spinning in a net direction simply because it is a magnet. We also know that the paper clips domains are spinning in random directions simply because it is not a magnet. The magnet has a magnetic field spinning around it, when the magnet comes close to the paperclip the domains of the paperclip start spinning in the same direction of the domains of the magnet. Now the paperclip is aligned with the magnetic field of the magnet. The paperclip now has a north pole and a south pole, the north pole of the paperclip is attracted to the south pole of the magnet, thus the paperclip sticks to the magnet!

From this question we can deduct a few things:

1)    The paperclip is now a magnet

2)    Opposite poles attract each other

3)    Like poles repel each other

Learning about magnets led us to talk about the Earth’s magnetic field. The Earth is actually a giant compass. The Earth, just like a magnet, has a north pole and a south pole, and all the charges move from south to north. The charges exit earth out the North Pole and circle back around earth into the South Pole. When the magnetic field surrounds earth, it actually protects it from harmful rays. We know this because all moving charges feel a force in a magnetic field when they are moving perpendicular to that field. For example, the northern lights, the northern lights only appear at the poles of the earth because that is the only place that cosmic rays are able to enter earth’s atmosphere. Thanks to earths magnetic field the cosmic rays can only enter the atmosphere at the poles because that is the only place that they are traveling parallel to the magnetic field. At the equator of the Earth cosmic rays are deflected because they meet the magnetic field at a perpendicular angle.

MOTORS:

One of the biggest activities of this unit was when we got to make our own motor! Making a motor was surprisingly a lot easier then I thought it would be. The materials we used were a battery, a magnet, a rubber band, two paperclips, and a coil of wire. The battery provided an electric potential difference so that there could be a current running through the coils. The coils, which were suspended above the magnet by the paperclips, would spin. The coils spun because current carrying wires are going to feel a force when in the presence of a magnetic field. The spinning coils were a motor. If we had attached wheels to either side of the wire then we would have a little car. Similarly, if we attached blades to the either end of the coils, we could have a blender or a fan. It is important to remember that with a motor we are putting electric energy in and getting mechanical energy out.

Right hand rules!

This unit we learned about two important right hand rules. The first tells us what way the magnetic field would wrap around a current carrying wire. The way your fingers wrap around your thumb represent the magnetic field while your thumb represents the direction of the current. The second right hand rule uses three fingers, your pointer, middle, and thumb. The middle finger represents the magnetic field; the pointer is the current, and the thumb the direction of the force!

A very similar concept to motors is generators, however they are the complete opposite. With generators we input mechanical energy and get electrical energy out of it. A generator works when a coil of wire is moved around a magnet or when a magnet is moved in and out of a coil of wires.

ELECTROMAGNETIC INDUCTION:

Electromagnetic induction is the reason that our credit cards work, metal detectors in airports work, and why stoplights change when cars drive up to them. When a car drives up to a stoplight there is a coil of wire in the ground. As the car drives over the coils of wire it induces a voltage. This voltage causes a current and this current acts as a signal telling the stoplight to change the light. The same thing goes for credit cards. A coil of wire is inside of the credit card machine. When the card is swiped the magnetic strip on the credit card changes the magnetic field and induces a voltage, which creates current, which acts as a signal and tells the computer the costumers credit card number.

TRANSFORMERS:

Transformers are those little boxes on appliances that either step up voltage, or step it down. In a transformer there is a primary coil and a secondary coil. The loops of the primary coil divided by the voltage going into the primary coils is equal to the secondary number of loops divided by the voltage going into the secondary coils. We know the power of the primary is going to equal the power of the secondary. However, depending on the type of transformer, the primary number of loops is going to be greater or lesser then the secondary number of loops and the opposite for the voltage. A mathematical equation could be written as 1 # of loops/1 volts = 2 # of loops/2 volts.

Some important formulas to remember for this unit would be:

P=IV (Power = (Current)(Voltage)

I=V/R (Current = Voltage / Resistance

*An important thing to remember for this unit was that when talking about generators, only Alternating Current works in order for electrical energy to be the resulting output. This is because with Alternating current, the alternating movement of electrons causes a change in the magnetic field, which is the catalyst for the flow of current. With Direct current, the electrons only flow in one direction, the lack of change would cause no change in magnetic field and a current would not be created.

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