The Top Ten Applications of Physics While Camping

Part of the reason physics is so phun is we can see it all around us.  I noticed physics this weekend, camping in the Great Smokey Mountain National Forrest. I also got 43 bug bites.  Below are the "The Top Ten Applications of Physics While Camping", organized by unit for simplicity.

Unit One: Velocity

1.  To get to the forrest, we had to drive about an hour.  The road was windy, and the speed limit changed often.  These two things meant that we were never traveling with constant velocity or acceleration, because both our direction and speed were changing almost constantly.

Unit Two: Newton's Second Law

2.  Newton's second law states that acceleration is directly proportional to force and inversely proportional to mass.  This was evident this weekend when we were skipping rocks in the stream by our campsite. The harder we threw the rocks, the faster they went, while lightly tossing rocks did not make them go as far.  Similarly, we could see this in the size of the rock.  The lighter rocks went faster than the heaver rocks.

Unit Three: Newton's Third Law

3.  We saw Newton's Third Law when we were hiking.  The 3rd law states that every action has an equal and opposite reaction.  When hiking up a step hill, just as we push the ground backwards, the ground pushes us forward.  However, we pushed the ground harder that the ground pushed us; this was the reason that we were able to climb the hill.

4.   Although our camping trip only involved hiking, some camping trips require rock climbing.  For rock climbing, nylon ropes are used instead of cotton or wool ropes.  This is because when a climber is falling, they will go from start to stop, no matter the surface they are landing on.  This change in momentum (p=mv) is represented by the equation ∆ p= p final - p initial, and is the same no matter the surface they are landing on.  Since the ∆ p is constant, and we know that ∆ p=J, we know J is also constant.  Since J is the same, the rope will increase the amount of time taken to stop as a result of the bounce.   An increase in time means a decrease in force.  More time=less force=safe landing.

Unit Four: Rotation

5.  Camping requires a lot of materials, and if you're backpacking, that can mean carrying a heavy pack.  If you're not balanced, a heavy pack can cause you to fall over-- what a disaster!  This disaster may occur as a result of torque (force x lever arm).  If your body's center of gravity is too high or off center, there could be a torque, causing you to fall.  For this reason, backpackers must widen their stance, thus widening their base of support.  This allows for the center of gravity to be over the base, greatly decreasing the likelihood of falling over because of a heavy backpack.

Unit Five: Work and Energy

6.  Closely related to hiking and camping in a literal sense, work and power are also related with Physics!  We can see machines, a tool that reduces the FORCE of an object (not its energy or work) in bear hangs, used to get food and toiletries out of a bear's reach.  At well established campsites, often park rangers will construct bear hangs with pulley systems, like shown below.  Pulleys are a form of machine that reverse the direction of the force you are applying.  This greatly decreases the amount of force, making the work (work= force x distance) easier.

Unit Six: Charges and Electricity

7.  Perhaps one of the most obvious needs while camping is a flashlight or headlamp. It was great learning about how batteries and lightbulbs worked, so that I could transfer that knowledge to my fellow campers.  Batteries use DC or direct current, meaning that the current flows in one direction from the high energy end to the low energy end.  When connected with a current carrying wire to a lightbulb, the circuit causes current to run thru the bulb, lighting the flashlight.  Who knew Physics made it possible to see at night out in the woods?!

8.  A not so fun part of camping is the threat of rain, specifically thunderstorms.  Lightening occurs when clouds in the sky rub together, and become charged thru friction.  This causes the top of the cloud to become slightly positive and the bottom to become slightly negative.  The ground then becomes slightly positive thru induction from the negative part of the clouds.  Since opposite charges attract, the positive charges in the ground start to creep up towards the negative charges in the clouds.  If the path is completed, energy is released in the form of sound (thunder), heat, and light.  

Unit Seven: Magnetism

9.  After a great weekend camping, we had to return to campus.  This required a second hour-long drive in the car, which is also powered by Physics!  Motors in cars, although more complex, rely on the same basic principles to work as the simple motors we worked on in class.  Motors require only two things: a magnet and a current carrying wire.  To work, motors rely on the torque felt by the current carrying wire's moving charges.  This force causes a torque, which spins the motor.  Motors convert electrical energy to mechanical energy, and are necessary to working cars.

10.  On the drive home, campers will undoubtedly pass a stoplight. The sensors that tell the traffic light when a car is waiting also has Physics to thank.  In this case, electromagnetic induction is our hero! Under the road, there are coils of current carrying wire.  When a car, essentially a giant magnet, passes over the wire, it changes the magnetic field of the wire.  This change in magnetic field induces a voltage, which causes a current, which acts as a signal to the traffic light.  Without electromagnetic induction, the smelly campers would be waiting forever!

So that is the The Top Ten Applications of Physics While Camping.  Although the bug bites and sun burns might fade, the memories and and physics lessons learned certainly will not.

Signing off for my last blog post-

Annie

Go Blues. Go Camping.  Go Physics.

Wind Turbine Blog

This week and last week, we worked in groups to make Wind Turbines.  In order to understand how wind turbines work, there are a few important "physics phacts" to know.

The wind turbine, although powered by wind, required a generator to induce voltage.  A generator consists of either a coil of wire spinning around magnets or magnets spinning around a coil of wire.  We choose to do the latter, as it is technically more simple.

Generators work as a result of Electromagnetic Induction, wherein the magnetic field of a coil of wire is changed as a magnet passes over it.

As far as our design goes, we modeled our generator from this website.  From the website, we knew we needed to purchase ceramic block magnets and a metal rod.  The red of the materials we were able to find in the classroom.

The turbine was not apart of the generator tutorial, so Claire and Holt took charge of the design.  We had initially planed to use wooden boards as the blades, but found that cut-up plastic bottles were also good to use.  In oder to make them spin, we had to tweak the angles of the blades, the directions, and the direction the wind was coming from.

The coils of the wire allow the current to flow.  It was important to note the direction of the wire's current, which is why you can see green arrows marked on the box.

The magnets, shown to the left inside the box, are what causes the change in magnetic field in the wire.  The metal rod is spun by the wind blades, which in turn spins the magnet.  The movement causes the generator to work.

Here is out wind turbine working!

In the end, we generated 0.008A of Current and .005V of Voltage.  Despite this very impressive result, we were unable to light the lightbulb because of the friction from our magnet.

Although significantly less stressful than the mousetrap car, this project did have its challenges.  Specifically, the copper wire.  Somehow, it became tangled, and made our lives very difficult.  In the future, I would work more carefully to ensure it did not become tangled.

As I mentioned above, we also learned the importance of trial and error in relation to the wind turbine blades.  Being able to adjust and readjust them depending on our needs became very important.

A huge lesson would also be to label the poles of the magnets.  Otherwise, you just might have to force two like poles together, which is not an easy task.

From this, I have learned how a generator works! I have also learned just how exact and frictionless it must be to produce a voltage, and not only that, but also a strong enough voltage to light a lightbulb.

Unit 7 Summary

In Unit 7, we focused on Magnetism.

The first topic of discussion was Magnetic Fields.  Magnetic fields are created by moving charges, and have a symbol of 'b'. Field lines travel from the South to the North pole inside the magnet, and from the North to the South pole around the magnet.  Magnetic fields are 3D.

Magnetic fields are the reason that like poles repel and opposite poles attract. When magnetic field lines are going in different directions, the magnets repel, but when the magnetic field lines are facing the same direction, the magnets attract.

Magnetic fields are also what allows a paperclip to stick to a magnet.  Before coming into contact with a magnet, a paperclip's domains (random clusters of charges all moving in the same direction) are unaligned.  When brought near a permanent magnet, the magnet's b causes the paperclip's domains to align along with the magnet's b.  The paperclip is now a magnet with its own North and South poles and magnetic field.  Because opposite poles attract, the paper clip sticks to the magnet.  

The Earth's magnetic field is interesting in that although geographic North is Canada, that region is home to the magnetic South.  Thus, the magnetic field runs from Canada (the magnetic South) to Antartica (the magnetic North) inside the Earth, and from Antartica back to Canada outside of the Earth.  This is the reason that the Northern Lights occur.  Cosmic rays can only enter the atmosphere when moving parallel to the Earth's magnetic field.  Should the cosmic rays attempt to enter the atmosphere at the equator, the Earth's b would deflect them back into space.

The last, and perhaps most obvious, part of magnetic fields are Compasses. A compass is simply a magnet that is free to move, and aligns with the direction of the magnetic field.

Below is a podcast made by yours truly about Magnetism.

The next topic was Forces on Charged Particles.  

The most important thing to remember is the Right Hand Rule.  Just like in the diagram, the thumb shows the direction of the force, the index finger shows the direction of the current, and the middle finger shows the direction of the magnetic field.  

Also in the realm of Forces on Charged Particles are Motors.  Motors consist of current carrying wire and a magnet.  They convert electrical energy into mechanical energy when the current carrying wire feels a force caused by the moving charges.  This force creates a torque, making the motor run.  For more on motors, check out my motor blog here. 

Finally we discussed Electromagnetic Induction.  This occurs when there is a change in the magnetic field of a loop of wire, and voltage is induced, which, in turn, causes a current.  This is seen again and again in our crazy, modern world, like in credit card machines, traffic lights, and metal detectors.  

Electromagnetic Induction also allows transformers to work. A transformer is a box with two coils of wire that can either increase or decrease voltage into an appliance. They work by changing the magnetic field of the primary coil through AC, which means that the b is constantly moving and changing.  This then changes the magnetic field of the secondary coil, which changes the voltage.  

Faraday's Law shows us that:

Transformers can be found on power lines, computer chargers, and appliance plugs.  

Generators also work because of Electromagnetic Induction.  Like a motor, they require a loop of wire and a magnet.  However, this is where the similarities stop.  Generators convert mechanical energy into electrical energy, and in this case, either the magnets are moving around the wire or the wire is moving around a magnet. 

Motor Blog Post

Motor Blog Post

For a functional motor, two parts are needed: a current carrying wire and a magnet.  To make our motor, we used a battery, copper wire, paper clips, a magnet, and rubber bands.  Below is a diagram of the motor. 

The battery in the motor supplies the voltage that supplies the current.  The current is carried up the motor through the paperclips, that both conduct the current and support the copper wire.  The wire conducts the current, and is shaped into a loop so it can be spun.  The current is also carried back down the other paper clip, touching the other end of the battery and completing the circuit.  The rubber bands tie it all together.

In order for all of this to happen, however, the current had to be carried all the way around and have the force be applied in the correct direction.  To ensure this occurred correctly, I had to be careful to scrape the insulator off of the wire in the correct place.  I scraped on only one side of the wire, and I did so on each end. This way, the current would be conducted in the proper places.

The motor turns as a result of the force on the moving charges in the copper wire.  This force is created by the magnet's magnetic field, or the magnetic effect of a given object.  When the copper wire is given current, it's charges begin to move, and are then affected by the magnetic field of the magnet.  This causes torque, and the wire loop to spin, and thus, the motor to work.

There are a variety of usages for a motor such as this one. Should wheels be attached, it could become a car.  Blades could also be attached, and a blender could be powered, or fan blades to cool off on a warm day.  

Below is a video of my motor working! 

Unit 6 Summary

This unit was all about charges and electricity.
First, we learned about charges.  There are three ways to make something charged: Thru contact (the transferring of electrons), friction (stealing electrons), or induction (charging without contact).

Friction is the reason that your hair stands up after taking off a winter hat.  When you pull the hat off, it steals electrons from your hair, giving your hair a slightly positive charge.  Since like forces repel, your slightly positive hairs stick up and apart in attempt to get away from each other.  

Friction also causes your clothes to stick together in the drier.  While being dried, they rub together, creating friction.  This makes some of your clothes to gain electrons, making them negative, and some of your closes loose electrons, making them positive.  Since opposite charges attract, the clothes stick together.

*Drier sheets eliminate this problem by absorbing electrons, making the clothes slightly positive and thus, repel each other.  

Both friction and induction causes lightening. First, the clouds rub together, and become charged through friction.  The top of the cloud becomes slightly positive, and the bottom of the cloud becomes slightly negative.  The ground then become positive through induction from the negative clouds.  Finally, the negative cloud charges and the positive ground charges creep towards each other through the air, and if the path is completed, energy (heat, light, and sound) will move form the ground to the cloud, creating lightening. 

A picture of induction at work from Paul G Hewitt

Lightening rods are placed on tall buildings in case of lightening.  Should lightening strike the building, it will be attracted to the rod, as charges are attracted to pointy objects. The lightning rod will run the charges along the building and into the ground, eliminating any damage to the building.  

Next, we talked about polarization.  When objects become polarized, the charges within the object separate, allowing one side to become positive and one side to become negative.   Polarization is the reason that plastic wrap sticks to ceramic or glass bowls, but not to metal bowls.  

When the plastic wrap is removed from its container, it becomes charged by friction and becomes slightly negative.  When it is brought towards the plastic or ceramic bowl,  the bowl polarizes.  The positive charges in the bowl move towards the negative charges in the plastic wrap, and the negative charges in the bowl move further away.  The plastic wrap sticks because the opposite, attractive force between the plastic wrap and the positive charges of the bowl is stronger than that between the similar, repulsive force between the plastic wrap and the negative bowl charges.  We know this due to Coulomb's law, which states that the smaller the distance, the greater the force, and the greater the distance, the smaller the force.  This is represented by the equation below.  Thus, the plastic wrap sticks to the bowl. 

Coulomb's law

The next topic is Electric Fields.  An electric field is an area of influence around a change.  Below is a helpful video, made by yours truly, about electric fields.

Electric Shielding is the reason electronics are encased in metal. While inside a metal box, the electric field is 0, meaning that a charge inside will not be pushed or pulled by outside electric charges.  Metals allow the charges to distribute evenly, therefore everything inside the box will be pulled in one direction but will have equal and opposite forces pulling them in the other direction.  

Capacitors are two oppositely charged plates.  

Camera flashes are an example of capacitors.  Two oppositely charged plates are continuously given charges, and the force between them continuously increases, as shown by Coulomb's law.  As the forces increase, the energy between them also increases.  When the plates are briefly connected, the energy rushes through the connecting wire and is released as light.  This process takes time, therefore flashes cannot work continuously.  

Before moving on to circuits, we learned some important vocabulary.

Voltage is a difference in electric potential.

Volts are electric potential.  It's symbol is "V".

Current is energy being carried through the wire with charges, and is caused by voltage.  It is measured in Amperes, and is represented by "I".

Electric Potential Energy is energy stored in electric fields.  

Resistance is the ability of current to flow in a wire.  A wire with a high resistance is typically long, narrow, and hot.  Lower resistance wires are wide, short, and cold.  Resistance is represented by the "R" and measured in ohms, the symbol Ω.

We also leaned some formulas.  

Ohm's law: I=V/R. Essentially, Current is directly proportional to Voltage and inversely proportional to Resistance.  

Power=Current x Voltage

Electric potential= potential energy/charge

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As seen above, when there is a difference in electric potential, voltage is created.  Voltage causes current, and when voltage travels through a closed, completed circuit, electricity is created! However, there are a few factors that affect current.  

Current is affected by Voltage and Resistance.  The more voltage, the more current.  The more resistance, the less current.  Resistance is affected by three things: thickness of wire, length of wire, and temperature of wire.  A long, narrow, hot wire will have a greater resistance, and thus a decreased current.  A short, wide, cold wire will have a lower resistance, and thus a higher current.

Lightbulbs burning out is directly related to current, voltage, and resistance.  When first turned out, the lightbulb's filament is cold, decreasing the resistance and increasing the voltage and current.  Often, it is this rush of current and lack of resistance that breaks an old lightbulb's filament.

Current, voltage, and resistance are also the reason it is dangerous to plug an American appliance into a European outlet.  American outlets are typically built with lower resistance, as they are plugged into outlets with lower voltages.  However, European outlets have a higher voltage, so when American appliances are plugged in, they are given more current than they can handle, often starting fires and power outages.

There are two types of wire currents.  Alternating currents, or AC, where electrons are constantly moving back and forth.  AC are what we use when we are plugging things into wall outlets.  Direct Currents, or DC, are when the electrons are moving in one direction.  This is the type of current that batteries use.

For more on currents and circuits, here is a helpful video.

Mousetrap Car Review

We recently finished our Mousetrap Car project.   It was full of physics, power tools, blood, sweat, and tears.  First, we'll go into the Physics concepts in the project.

Friction is a very important part of this project.  Friction is effected by two things: Weight and
Different Surfaces. If the Friction is too small, there will not be enough torque. Too much Friction, there will be too much torque.

All three of Newton's Laws are represented in this project.

Newton's First Law states that an object at rest will stay at rest, while an object in motion will stay in motion, unless acted upon by an outside force.  This is seen in the project in that the car, if in motion, will stay in motion unless a force pushed it backward.  In this case, the outward force is friction.

Newton's Second Law states that Force is equal to Acceleration x Mass.  This can be rephrased to Acceleration= Force/Mass.  In the car, the force, or the snap of the mousetrap, causes the acceleration.  The bigger the force, the greater the acceleration.  However, too much mass will lower the acceleration.

Newton's Third Law states that for every action, there is an equal and opposite reaction. For the mousetrap car to work, the car pushes the ground back and the ground pushes the car forward.  This is the very force that allows the car to move.

Energy wise, pulling the trap back creates Elastic Potential Energy. When the trap is released, the PE is converted to Kinetic Energy, which causes the axel to turn.  Storing energy in the spring and using it's torque to create a force will cause the axel to move.  This is because the force is perpendicular to the axel, and thus the direction. It is important to note that the amount of energy in the car remains constant throughout the whole expedition. 

By adding a lever arm. we do not increase the force- rather, the lever arm increases the time and distance that the Force is acting on the axel.

THE CAR
Below is a video of our car.  It completed the required distance of 5 meters, and came in 3rd place with a time of 3.77 seconds.
 
With the picture below, we can see how these physics concepts apply on the actual car we made.

Starting with the wheels, you can see that all four wheels have electrical tape around them. This is to create friction.  Although in other places in the car, Friction was our "worst enemy",  Friction between the wheels and the ground is necessary for the car to move.  Also something to consider is the size of the wheels.  All wheel need torque (force x lever arm) to turn.  Larger wheels have a big lever arm, creating a big torque.  Larger wheels will also have a smaller rotational velocity.  Small wheels, on the other hand, have a smaller lever arm and thus a smaller torque. They also have a high rotational velocity.  However, all of the wheels of the car will have the same tangential velocity. 

Next, the frame.  A light frame is necessary, just as we talked about above, in Newton's Second Law. A frame too heavy means that the car cannot accelerate.

By using the formula velocity= distance/time, we can see what the average velocity of our car was.  It went 5 meters in 3.77 seconds, meaning that its average velocity was 1.326 m/s.   An important thing to note, however, is the we aren't able to find the amount of work done by the spring on the car.  This is because the spring's force and direction are perpendicular, meaning that no work is done.  Without force, we are unable to find the Change in Kinetic Energy, or the Potential Energy stored in the spring.  We also cannot calculate the amount of force exerted on the car to accelerate it, because again, the force and direction are not parallel.

REFLECTION

This was one of the more frustrating projects I have ever completed.   However is was the difficulty that made the completion of our car even more satisfying.   Our design varied greatly throughout the process.  The most notable changes are those made with our frame and our wheels.

The wheel change occurred after I tried to set our car off and it flipped over completely.  This was because our back wheels were significantly larger than our front. We rectified this issue by changing the back wheels from larger wooden disks to CDs.  This allowed for a more balanced car.

The most drastic change was the shift we made just two days before the car was due.  We noticed that our axles were crooked due to the way that they were attached to the base of the mousetrap.  We did some research, and realized that we should increase the distance of the wheels and also create a hole for the axles, allowing them to turn more easily. This turned out to be the best decision we could have made.   

Aside from the structural issues mentioned above, we had major problems getting our car to move by itself.  Our vision of a lever arm attached to a string which would wrap around the back axle never changed, but we had to make lots of little adjustments.  This problem greatly hindered the proformance of our car initially, but we were able to rectify this by lengthening the lever arm and shortening the string.  This allowed our car to have enough power to complete the five meters.

To make our car go faster, I would have done a number of things.  First, I would have made all of our axles slightly smaller.  This would decrease the amount of friction between the axle and the frame, allowing for more speed.  I also would have made a lighter frame, because as we stated above, a heavy frame decreases the acceleration.

If we were to do this project again, I would do more preliminary research before starting.  Niara and I had a lot of confidence, and that made us think that we could complete the project without any resources besides ourselves.  I think our process would have gone much more smoothly had we consulted books or websites.

Unit 5 Review

Unit 5 was all about the relationships between Work, Power, Kinetic and Potential Energy, and Machines.

Work is equal to F x d.  Work is measured in Joules, and in order for work to occur, Force and Distance must me parallel.  Work is not done if the two are not parallel.

Also in the realm of Work is Power, which is equal to work/time.  As Ms. Lawrence said in her video, Power measures how quickly work is done.  Power is measured in Joules/time, or Watts.

Kinetic Energy is the energy to do work.  Kinetic Energy=1/2mv^2, and is equal to Work (Work=Change in KE).

This video is helpful, if not slightly strange.

 An importance piece of understanding is how it relates to airbags.  Airbags help to keep us safe, because we go from moving to not moving, no matter how we were stopped.  Therefore, the Change in KE (Change in KE= Ke final- KE initial) is the same with or without the airbag.  The change in KE is equal to Work, meaning that work is consistent as well.  Work= F x d.
The airbag increases the distance between you and where the force is applied, lessening the force. Small force=less energy.

without airbag: work = F x d 

with airbag: work =  f x d

Potential Energy is the energy of position, and is equal to (m)(g)(h).  An import thing to note is that movement is NOT NECESSARY to have energy.  In order for there to be potential energy, there must be height.  

Max KE= Max PE is another important part.  It states that there is always going to be the same about of energy at the beginning as there is at the end.  This is why Roller coasters work.  

The Law of Conservation of Energy is the law that states work in = work out.  

Machines decrease the amount of force needed for work to occur.  This is done by a number of simple machines, including ramps and pulleys.  

Machines, however, are not completely efficient.  Some of the energy is exerted in t

This is a very helpful video, and has a catchy (yet repetitive) tune.