may the forces be with you, balanced - Unit 6

These are pictures of me dog sledding a couple spring breaks back in Whistler. It was super duper fun, so if you are in Whistler or anywhere where you can dog sled, I highly recommend it. The dogs are super cute too!

Let's look at the forces on the sled. Because it is on the ground, there is a normal force exerting upwards. They also have weight, which is pulling them to the ground so they don't fly away. Even though these two forces exist, they cancel each other out, so one force isn't acting more than the other one, leaving it balanced. Because the dogs are pulling on the sled, there is tension pulling the sled forward and tension pulling the dogs back. The last force that exists is friction. Friction is what makes the dog sled slow down and come to a stop. Although you cannot see in this picture, the dogs are not keeping a constant velocity, as they constantly accelerate the further they go. This means that tension and friction are unbalanced, because there is more tension making the sled accelerate.

when push comes to shove - Unit 6

Now that I understand forces with two objects a little more, I am aware that I made the learning process a little more difficult than what it is, and in reality, it is much more simple. The trick is knowing if the objects are in constant velocity or in constant acceleration. By knowing which it is, you can determine which object is exerting a greater force. If the velocity is constant, you know that the blocks are exerting an equal force. This is because the force from the push for the 45 kg ball becomes the normal force for the 10 kg ball, making them have the same force. Although the push isn't directly going to the smaller ball, because the big ball has that force and it is touching the smaller ball a normal force going left is created for the smaller ball. Friction on the smaller ball and friction + normal force on the bigger ball pull back on the balls, preventing it from accelerating, which is why it has a constant velocity. Although the balls are going to the left, they have a constant velocity and have equal forces on them. If I were to draw a force diagram for each of the balls during the motion it would look like this:

This is a picture of me holding a balloon blowing away (this was the only picture I could find that had tension! Because balloons are filled with helium, it is very light, lighter than air, which is why it wants to float up. I tried challenging myself, and hopefully it's correct!) We know that there is tension going in the downward direction because the object is floating upward and it is attached to the string underneath it. Since air is heavier than the helium in the balloon, there is very little weight. The tension is what balances the weight so the object stays idle. Because the object is hanging by a string and not sitting on a surface (unlike the other picture), there is no normal. Lastly, there is another force, wind that is making the balloon blow in a certain direction. If I am correct, the diagram should look like this:

ukerub technique - Unit 5

In class today, we went into depth about Newtons three laws of motion, free body diagrams, and vectors. My last blog post talks a lot about the definitions, but for this post i want to see how they apply to daily life. In class, Mr. Blake mentioned how when a car veers to the left, the people in the car actually lean to the right. This was something I had always learned about, and just now I realized that it's physics baby! This is my explanation of what goes on in the car when this "jello" game happens. Let's say when in the car, it is going a constant velocity, so therefore it isn't accelerating. However, when you turn your car to the left, you are accelerating because you are changing the direction (assuming that you are not changing the velocity when you turn, even though you should decelerate for safe driving). Because of Newtons first law of motion, we know that an object in motion will stay in motion unless acted upon by an outside, unbalanced force. So when driving in a car, your butt and feet move the same way the car moves because it is connected to the car, but your head and most of your body isn't, so inertia makes your body want to still move forward, when the car is moving left. Thus, you move in the opposite direction you are going to continue going where you were going before the car changed directions.

standard physics - Unit 5

Newtons three laws of physics:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. 

II. The relationship between an object's mass m, its acceleration a, and the applied forceF is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.  

III. For every action there is an equal and opposite reaction. 

The first of Newtons laws rooted from Galileo's concept of inertia. This law is stating that an object in motion will continue to move, unless something (a force) is preventing it from doing so. 

     For example, if I were to push a binder across the table, technically it would keep moving if friction didn't exist. Or it could slide off the table and hit the ground where it would stay because of gravity. If it weren't for this law, you could never move an object without losing it forever. 

Basically, the second of Newtons laws is telling us that the acceleration of an object depends on the net force acting on the object and its mass. As the force (like friction or gravity) increases, the acceleration increases; as the mass of an object increases, the acceleration of an object decreases. 

    For example, if an object has a net force of 20N, and a mass of 4 kg, it's acceleration is 5 m/s^2.

Lastly, Newton's third law indicates that in every interaction between two objects, there is a pair of forces acting upon it. The sizes of the forces for each are equal and the direction of the forces are opposite. All you need to remember for this law is that forces always come in pairs and there is an equal and opposite action-reaction. 

     For example, think of a magnet. On a magnet, there is a positive force on one side, and a negative force on the other, meaning that the direction of the forces are opposite. We know that the two forces are equal because if there is nothing magnetic on a table, you can have the magnet facing up or down (positive or negative). If the forces weren't equal, one side would always be facing up. 

 This is the extent of my knowledge, hope it makes sense!

sensei's last words - Unit 4

 Projectile motion gets even more complicated than the vegas rule, and 2 dimensional analysis when angles are added to the word problem. But not to worry, if you know your trigonometry than it's quite easy to understand.

Here is a problem I made up, that involves angles in projectile motion:
   
          If a girl jumps off a rock ledge 5 meters high into a pool with a velocity of 2m/sec at an angle of 5˚, what is the initial horizontal and vertical velocity, how long is the girl in the air, and how far horizontally will the girl land in the pool?

First you have to do the following trigonometry to get the initial horizontal and vertical velocity.








Once you know the horizontal velocity, you can plug that in the XY table as the initial and final velocity on the x-axis. The vertical velocity can be plugged in as the initial velocity on the y axis. Next, we have to remember our rules from yesterday, and find the time in the aYer. That can be done with the "DAT" equation: Dy(m)=1/2 ay (m/s^2) t^2 (s) + Voy (m/s) t (s)
or
5m=1/2(-9.8m/s^2)t^2(s) + 0.17 (m/s) t
5=-4.9t^2+0.17t
4.9t^2-0.17t+5=0
(do quadratic formula)
t=1.03

Once you know the time, find the distance of the x-axis using the DAT equation again.

D=1/2(0)1.03^2+1.99(1.03)
D=2.58
She went 2.58 meters horizontally into the pool.

Summary statement, a girl jumps off a rock ledge 5 meters high into a pool with a velocity of 2m/sec at an angle of 5˚, what is the initial horizontal velocity of 1.99 m/s and an initial vertical velocity of 0.17m/s. The girl was in the air 1.03 seconds, and jumped a horizontal distance of  2.58 meters.

that's why i can flip a quarter in the car without it hitting my face! - Unit4

Projectile motion took me such a long to understand, so here's my post for as far as i know!
To prove my understanding of projectile motion, i created my own word problem:

An airplane flying 1000 m/s dropped a parachuter and he reached his landing spot at sea level, 600 meters from where the plane was. How high up was the plane?


Answer, 17.64 meters above the ground.

How to solve this answer: First you have to write down the givens in a format showing the x and y axis. You must remember to follow the "vegas rule" (whatever happens on the x or y axis stays on the x or y axis respectively...). You should have a table of givens that look like this:


X-axis table explanation: the initial and final velocity is the same because the plane is not accelerating.  The plane isn't accelerating because, because it's velocity isn't changing.

Y-axis table explanation: the original velocity is zero m/s^2 because the parachuter was sitting in the plane, he wasn't moving and therefore didn't have any speed before jumping off. Acceleration is -9.8 m/s^2 because the parachuter is being pulled by gravity (-9.8 m/s^2) in a downward motion (according to the positive and negative is in arrow drawing.)

In order to find the height of the plane, we need to find the time it took first. Time is equal n the x-axis and y-axis, because we learned that objects travel at the same speed no matter the direction they are thrown at.

Finally, to solve the equation, use the DAT equation, or d=1/2at^2 + Vot using the givens from the x-axis.
You should get 600m = 1/2 (0m/s^2)t^2s + 1000t

600 = 1000t, t= 0.6
Once you get the time, you can plug it in the DAT equation again, but this time use the givens from the y-axis.
You should get Dm= 1/2 (-9.8m/s^2) 0.6^2s + 0t
 D=1/2(-4.9)(3.6)
D = 17.64 meters. 

This is not a picture of me parasailing. I'm parachuting.

The height of the plane was 17.64 meters when the parachuter jumped off!

Q1 accumulative

We learned a lot in 2 weeks! I never imagined knowing so much physics in such little time.

Unit 1: The first thing we did, was compare mass, angle and length to a pendulum. We did this by doing the "Period of A Pendulum Lab", and discovered that angle and length have a direct relationship, whereas mass and periods have an inverse relationship. All of these reltionships can be drawn out on a d-t graph, which measures distance vs. time. Next we learned the 5 different types of graphs. 1) no relationship [line is horizontal], 2) directly proportionate [linear diagonal starting from origin], 3) inversely proportional [a curved line starting at a relatively high and ending at a relatively low distance], 4) proportional to the square of x [the right half of a U shape] and 5) proportional to the root of x [the top left side an o]. A few more things we learned (and didn't go into great depth on) are scientific notation, the difference between accuracy and precision and dimmensional analysis.

Unit 2: Unit two was all about kinematics and motion maps. Using many key words, we learned how to graph the motion of an object given its' description. Some key words include scalar, vectors, displacement, instantaneous speed, instantaneous velocity, constant velocity, acceleration, avg. speed, avg. velocity, velocity, and position. The most important thing we learned, is probably the 3 graphing rules; The slope of a DT graph equals velocity, the slope of a VT graph is acceleration and the area under the curve of a VT graph is displacement.

Unit 3: Unit three was still about kinematics, but focused on a certain type of it, acceleration. We learned from the acceleration activity lab that the relationship between position and time is position equal time squared. After knowing how to graph a VT and DT graph from the previous unit, we learned how to create an acceleration graph using the VT graph. If the slope of a VT graph is going negative at a constant rate, then there is a negative horizontal line in the AT graph. Same thing for if it is going at a positive constant rate, the slope would be horizontal at a positive velocity. If there is no slope in the VT graph, this means that it is not accelerating, which means there is a horizontal line lying at zero on the AT graph. We also did a couple of labs on free falling objects. When you are throwing an object in the air, it is accelerating downward so the velocity slows down the higher it goes up.  When the object is at the highest point, it is no longer accelerating, so the acceleration is zero. Then it is falling back down at a relatively similar time to when it was thrown up. The object accelerates as it moves closer to the starting position. So when you throw the object and when you catch it is when the velocity is the fastest. Lastly, we learned that earth has a gravitational pull of about 9.8 m/s^2, which is why the object slows down as you throw it up. Because you are throwing it up (away from the ground), gravity wants to pull it back down, so the object is accelerating in the negative direction, slowing it down to a stop.

That's about it, we learned all this in 10 days; it was a whirlwind!!

The earth moves at a constant velocity of 107,300 km/h around the sun. It does not accelerate in the positive or negative direction.