Final Mousetrap Car Report

The mousetrap car like physics is a very frustrating. This annoying contraption somehow outlined almost everything we've learned so far in physics. This car used all of Newton's three laws. It used newton's 1st law in that and object in motion tends to stay in motion and an object at rest tends to stay at rest. This law applied to actually getting the car to move and to do this you needed a certain amount of friction to actually develop a movement and not too much friction because this would stop the car. To create friction we put tape on our wheels but only the back wheels cause too much friction would render the car's movement. Newton's 2nd law acceleration = force over mass or A=f/m. This meant that in order to accelerate more we needed to get a good force over a small mass. The smaller the mass the larger the easier it is to accelerate. In order to to this we tried to use light efficient materials. And lastly Newton's 3rd law, every action in an action reaction pair has an equal and opposite reaction. The wheel's push the ground back and the ground pushes the wheels forward. Avoiding centripetal force which did become a problem for Lincoln and I. The wheels were the biggest struggle for Lincoln and I that is because the wheels deal with the delicate balance of friction. We tried a variety of tapes to create friction but they were all too much, so too much friction was definitely a great disadvantage. We first started off with wood wheels that created to much friction so we switched to CDs, theses CDs created just enough friction to move and the right amount to keep moving. We had a pretty large force on our car so we used larger CDs in order to cover a good distance. This is because CDs are large and the diameter (lever arm) of the wheels increases the torque. However big wheels are harder to get spinning so we needed a lever arm to create enough force to spin the wheels and keep them going. When it comes to energy, the mouse trap car our potential energy came when we winded back the mouse trap and axel, but when we let the mouse trap do its work the energy becomes kinetic. Winding the axel more created more potential energy that would become more kinetic energy, this was very important to the function of our car. Because we tied rope to the axels we wanted to have more rotational velocity to compensate with our wheels. I knew that we needed to create a lot of rotational force to get these wheels moving to do this we created a lever arm as an attempt to increase the tangential velocity. This helped get our big wheels moving in order to increase the distance. Because the spring is going up and down and the car is going forward, these two forces are perpendicular therefore work can't be calculated. We can't calculate the potential energy in the spring because we can't calculate work. There is energy stored in the car ( potential) but when it begins to move it becomes kinetic.

 .83 m/s

     Reflection: Our original design featured a tapir wheel design big in the back small in the front and a mouse trap with strings attached to the axel. We initially had trouble with the cart because the axels had too much friction in it. To solve it I took the tap off the axels to where it went in the car and it worked wonders. Friction became my arch enemy during this project. Ugh I hate determining the right amount of friction to use our friction problems initially kept our car from moving. If I could redo this I would use lighter wood more glue and CDs would be my wheels from the beginning. I would also do more research to make the most efficient model ever, I would import my materials from abroad and grease my axels.

Unit 5 Blog Post

Unit 5 was a pretty equation heavy rather than conceptual. We first began by going over work. Work is force x distance, but the force and distance both have to be parallel or no work is being done, and the only distance used is vertical. We introduced work with a experiment in which we walked, and ran upstairs. The point of this exercise was to understand that no matter how fast you reach a fixed height you will be doing the same amount of work because work is simply force times distance. But when you added weights you changed the work because you changed the force you had to carry in that upward distance. In this experiment we were not just introduced to work but also power. Power is work over time. Meaning when we ran up the stairs we had different power than from when we walked. We actually had more power when we ran, this is because the time was less and when you divide the work over a smaller time you will have a larger result than a larger time. Power is measured in watts. Hmmm... Watts and Power? Sounds familiar. Oh yeah that is because when we hear power we think of horsepower. Horsepower is what they rate an engines strength and speed on. A single horsepower is 746 watts and when running up the stairs I was able to produce a full horsepower.
     Our next topic was Kinetic energy (KE) and it's relationship to work and Potential energy (PE). Kinetic energy is the energy and object has while in motion. Or work in motion. KE= 1/2mv^2. KE and work are related in that change in KE(or delta KE) = work. My podcast group chose this topic and here is our video for it...

Our video showed Luke's car changing velocities and therefore kinetic energies and their respective differences and then we found the distance it would require to stop by using the equation Change in KE= work. Because the velocity is the KE equation is squared the stopping distance will be squared. say you have a velocity of 2, your stopping distance would be 4, 3 would be 9 and so on. We used the stopping distance as our bread and butter in explaining the relationship between Kinetic Energy and Work. Potential energy is the energy that depends on an objects height. PE=mgh. An object will have high PE at a large height and zero PE on the ground. Another group in our class did a video on PE relationship with KE. 

They use a pendulum to describe the relationship between potential and kinetic energy. PE and KE are always conserved. The max energy will always be the su of KE and PE. A resting object at its peak will always have it's highest PE and lowest KE (0). At the bottom it will have its highest KE and lowest PE (0) and will reverse when it gets back to the peak.
    The last key concept we learned was machines. Machines help us by directing the work we do on an object more efficiently. To carry a 1N box 1m up we can't change the work done, but we can decrease the amount of force we put in. We can do this because work=f x d, and we can change the distance it takes us for us to get to the target distance. We can do this because if we are trying to get a box 1m high the only thing important to work is the force and upwards distance, but we can increase the horizontal distance up toward the vertical height we want to reach and fraction the force we exert. Ramps, Pulleys and levers are machines that do such things. By increasing the D in we are able to decrease the f in. This is how machines help us, not by decreasing work, but by making more efficient use of our force put in.

unit 4 blog post

I think unit 4 was my favorite physics lesson so far. Every lesson in physics is applicable to real life but I felt as this unit hit my areas of interest. We kicked of the unit by first going over torque. Torque at a mathematical level is force x lever arm. But scientifically torque is the tendency to rotate at an objects axis of rotation. You can increase torque on objects to help you achieve tasks as well. This video gives examples on how to... 

In class we had a mass of meter stick challenge in where we were assigned a meter stick with a 1 kg weight attached to it. To find the weight we had to find the center of mass of the meter stick without the weight attached. We accomplished this task by finding the torque on both sides of the meter stick while balancing it with the weight attached. 

All objects have a center of gravity/mass. We can manipulate the distribution of our mass to keep our center of gravity from rotating. In football linemen crouch with their legs far apart and knees bent. They do this and it makes them harder to rotate or be knocked over for two reasons. Spreading ones legs widens their base of support which gives more space for their weight to go over. An object looses balance when it's weight is not over its base of support. The bent knees keep a person's weight close to their axis of rotation and this keeps them closer to the ground and base of support which makes falling over more difficult. This video explains the application...

Objects rotating  have two velocities, tangential and rotational. Tangential velocity is the distance cover in a spin while rotational is the amount of spins over given time. We see these in gears. You can have tow gears connected, a small and large, and they will both have the same tangential speed but different rotational velocities. This is because they both spin the same amount of notches per second but the smaller gear finishes a rotation quicker. Th wheels of train tracks are tapered so they have varying rotational velocities and because the train spins on wheels, it is the rotational velocity that controls the speed and direction of the train.
     We also learned about rotational inertia. As an object spins, the distribution of it's mass can change it's rotational inertia. When an objects mass is closer to it's axis of rotation it has less rotational inertia and spins faster. This is how ice skaters are able to control the rate at which they rotate. My group video explains how rotational inertia works and how it is conserved.

The last thing we went over was centripetal force which literally means center seeking. This force is by the moon stays revolving around earth. Earths gravity acts as a rope pulling the moon toward it so the moon does crash off somewhere. Say you have a bucket of water and rope attached plate. You put the water on the plate and start to spin it around your head. The water does not spill because the centripetal force keeps it towards the middle of the cup.

Mass of Meter Stick

In class Monday we were assigned a meter stick with a weight strapped to the end. Every meter stick was a different weight and all we knew was the mass of the weight. The objective of the meter stick project was to find the weight of the meter stick just using the provided weight. Ali and I were grouped together and knew that the first peace of information to jot down was the center of gravity on the stick and the distance from the center of gravity and the end of the meter stick. This will be one of the lever arms. We can now find the torque, because torque= lever arm x force. The center of gravity was at 50 cm and the weight was 1 kg. To calculate force we multiply gravity by mass and we get .98. The meter stick with the weight balanced at 30 cm so the lever arm was 30 cm. Force .98 x Lever arm 20 cm, this will give you torque. And because the object is balanced  the torques on both sides must be equal. So .98 x 30 cm = the distance between the balancing point (50cm) and the center of gravity which was 20 cm. So .98 x 30 cm = 20 times lever arm (unknown x). When solving for x you get 1.47. So now you divide 1.47 by .98 and we got 145 grams. The actual weight measured on a scale was 150 grams. For future experiments to get more accurate results we could find a better table to measure the center of balance and more accurately measure center of gravity. This experiment  helped me by giving me a physical example of gravity and torque on objects. I know know how to use equations for torque to find the weight of objects.

Center Of Gravity

This video gives a blunt simple definition of center of gravity that is easy and understandable. The experiments they do are similar to one we has done in class they talk about how you must keep your weight over your center of gravity to keep balanced. They place emphasis on where your weight is distributed which is very important in understanding center of gravity, talk about staying low to keep your mass close to the center of gravity. Also its a sick cheesy physics video what could get better?

Torque

I like this video because it is short sweet an applicable. This video gives a simple yet in depth explanation of torque while giving everyday examples of how we see torque in everyday life. When turning a wrench the distance the shaft of the wrench is from the axis of rotation allows you to assert more force on the bolt. A lawn mover allows more rotational speed which allows it to cut through thicker grass. Torque is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist to an object. I no know what torque is all about and can recognize it wherever I go. 

Unit 3 Blog post

Unit 3 began with the introduction of Newton's 3rd law which states that every action in and action reaction pair has an equal and opposite reaction. Example when you run you push the ground back and the ground pushes you forward. This law is what allows us to move. In a horse carriage the force the horse pushes the ground with is stronger than the force the wheels push the ground with. This push against the ground creates  friction and the wheels have less friction which allows the carriage to move forward. We then moved on to the subject of tides. 

This video is a very good demonstration on how the moon's cycle affects the tides on earth. To get a visual moving cycle helped me understand what exactly happened. This video also differentiates the high and low tide cycles by color. As you can see the high tide starts off as light blue and pulls in as the moon shifts spots, same goes with the dark blue tides. It was very helpful to see the movement of earth's bulge during a 28 day cycle. 

Now this video gives more specifics on how the forces are pulling earth and it's tides. The side of earth directly facing the moon has the largest gravitational force(side 1). The side directly across earth has an equal and opposite force(side 2). Given the equation for the force between two objects F= g(m1xm2)/d^2, side two has less distance between the two objects (earth and moon) meaning there is a larger force. Distance and force are proportional. Side two has an larger distance and a equal and opposite force in the other direction. Say the force between earth and side 1 is 5, the force between earth and side 2 would be -5, a negative force simply means in the opposite direction.  This is why we see equal stretches in bulge from both sides. The earth rotates on an axis so every 6 hours the tides will change from low to high tides. Tides are highest at the new and full moon. These high tides are spring tides the force between earth and the moon are at their greatest. When the moon is half waxed and half wained the tides are still pulled by the moon but are still relatively low. The tides draw from the high tides on the other sides and add to their low tides creating neap tides. Neap tides are always slightly higher than the low tides. It is important to notice that even thought the force of the sun is stronger than the moons that because the greater increase in distance that we mostly feel the moons instead. After learning about tides we moved on to conservation of momentum. Momentum is the change in force over time. impulse is the change in momentum.  In a collision the change of momentum is the final momentum minus the initial momentum. In order to find momentum you must multiply an objects mass by its velocity.  Impulse is measure in Newton's seconds and momentum is measure in kilograms meters per second. To find the exact force at a period in time you take the change in momentum over the specific time.