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. 

Unit 2 blog post

Unit 2 was based off of Newtons 2nd law and how objects move through air. Newtons 2nd law says that acceleration is proportional to force and acceleration is inversely proportional to mass. This can be written out as a=f/m which explains all of Newtons second law in symbols. This law was tested in our cart pulley experiments. To test force being proportional to acceleration (a~f) we put more weight on the pulley(force) and kept the cart weight the same. We noticed that the more force added the faster the cart would accelerate. We tested the second part of Newtons 2nd law by keeping the pulley weight constant but adding more mass to the cart. The more mass added to the cart the slower the acceleration. Through these experiments we confirmed Newtons second law. When learning how objects move through air, we studied skydiving, and variations of free fall. Skydiving is when an object is falling through air accounting air resistance. When falling with air resistance an object will fall much differently than in free fall. Heavier items have more f-weight therefore more f-air resistance. This makes then reach there terminal velocity faster and this is why to a point heavier items fall faster than lighter ones. Terminal velocity is when an object stops acceleration and it's net force reaches zero during the fall. When parachuting a person reaches two terminal velocities. The first one is when they first reach 0 acceleration and net force, their acceleration and net force are downwards. When a person pulls the cord for the parachute the f-weight and f- air become unbalanced, the acceleration is directed upwards and the object begins to slow down. When falling straight down without air resistance only the force of gravity is acting upon you. The force of gravity speed your fall up by 10m/s. So if you are going 50m/s on the 4th second, you will be going 60 m/s on the 5th. When throwing an object straight up the idea is similar except when the object travels up it slows down by the force of gravity by 10m/s until it reaches it's peak in where it is not accelerating at all then it falls and proceeds to accelerate by 10m/s. This video clears up common misconceptions about falling objects in free fall. The man walks around asking people on their thoughts about what would happen if you dropped two equally sized  balls with different weight from the same height. The point of this demonstration was to explain that weight does not change the speed of an object in free fall because the both will have the same acceleration. The only thing that affects the time an object takes to fall in free fall is the height and acceleration of an object. If you were to shot a bullet and drop a bullet shell from the same height, they would hit the ground at the same time because they have the same acceleration and height. This video reconfirmed a topic I struggled with earlier on this unit. It was also interesting to see how my initial thoughts on free fall matched the randomly sampled pedestrians in the videos. What calculates how long the object will stay in the air is the height it reaches or begins at. Any two objects with the same acceleration and height will hit the ground at the same time. When objects are launched at an angle calculate the time will be the same as throwing straight up(twice the time it takes to reach the top). The horizontal velocity will remain the same while the object is in the air. The vertical velocity will decrease by 10m/s each second on the way up to it's peak and increase by 10m/s each second down from the peak. To calculate the horizontal velocity you use v=d/t. To calculate vertical velocity you find the velocity relative to the initial velocity and time the object has been in the air. To calculate actual velocity you create a triangle.  Using the horizontal and vertical velocities as the bases and to find it you solve for the hypotenuse. This calculates the velocity at that second. The same process is doe when calculating speed on falling at an angle. The vertical velocity and height an object reaches determines it's time in the air.