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. 

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.
http://tides.mobilegeographics.com/locations/2080.html here is a link to Galveston beach in Houston, Texas. Currently this beach is approaching high tide and will be until 11:45 pm. Currently the moon phase is approaching the last quarter meaning it is about to be in neap tides. 

This video very clearly explains how to find the angle and direction of vectors. The real life example helps this idea stick. Also it is good to get a visual of how to calculate the angle and direction, I feel that I can now apply this to a problem on paper. The reason this video was made was to explain the math behind vectors for beginners like us. This video was not very interesting but clearly and quickly explained the concept which was something I liked.