Thursday, September 25, 2014

Unit #1 Summary

In this unit I learned...
1) about inertia. No object will move on its own accord. However, If an object starts moving and there is no outside force to prevent this movement such as friction, gravity, ect. it would keep moving forever and it requires the same amount of energy to stop something and to start something. This all means that objects are 'lazy' and like to stay where they are. In a nut shell, inertia is the fact that no object moves on it's own accord.
   Newton's First Law supports the idea of inertia by stating that all objects at rest stay at rest and all objects in motion will stay in motion unless acted on by an outside force.
   We learned about these concepts in many ways. In one lesson, we watched a cart that had a ball in it move. At some point, the ball was popped up and out of the cart, and although the cart was moving foreword and the ball was launched up, the ball landed back in the cart. This occurred because both the ball and the cart were moving foreword. When the all was popped up, it continued to move foreword because as Newtons law states, objects in motion stay in motion, and it landed back in the cart. This same exact concept can be seen in many different everyday ways including the quick removal of a table cloth out from under dishes when the dishes stay in place (objects at rest stay at rest), as well as a coffee cup spilling or falling when a vehicle stops or starts (objects in motion stay at motion), and many more.  
        
2) When we rode the hovercraft, we learned about inertia and Newton's First Law but we also learned about equilibrium and net force. Net force is the total forces being put on an object that makes the object move. For example, if one person is pushing a box with a force of 5 newtons to the right, and someone joins them and pushes the box the box to the right with a force of 13 newtons, the net force would be 5+13, or 18n. However if someone was pushing a box to the right with a force of 5 newtons, and someone else is pushing the box to the left with a force of 13 newtons the net force would be 13-5, or 8.

Equilibrium is when the net force adds up to zero newtons. This can mean that the aforementioned box is stationary or that it is moving at a constant velocity. If it is moving at a constant velocity of 15, for example, the friction pushing against the box would be 15. Since equilibrium requires a net force of zero and 15-15=0, the box would be in equilibrium.

3) If we wanted to know how fast this illusive box is traveling, we would need to find the speed or the velocity. Speed is simply the measure of the distance an object travels in a designated amount of time.   Physicists usually measure speed in meters per second or m/s. Velocity is the same as speed, except it requires a specific direction. For example, you could say that as a race car rounds the track it increases its speed but you could not say that as a race car rounds the track it increases its velocity. Velocity is represented with arrows called vectors that represent magnitude and direction. The three ways to change velocity are changing direction, speeding up, or slowing down.
The equation for constant velocity if we want to know how fast an object is moving is v = d/t. The equation for constant velocity if we want to know how far an object moved  is d=vt.
Here is a video my classmates and I made about velocity:
4) If we want to know how fast an object is picking up speed, we need to know about acceleration. Acceleration is simply a change of speed like slowing down or speeding up. If a car is moving at a speed of 4m/s and in the next second it is moving at a speed of 8m/s, and in the next second the car is moving at a speed of 12m/s the car has accelerated by 4m/s^2 every second. This means that the car has constant acceleration. If a car is moving at 2m/s one second, 6m/s the next second, and 13m/s the third, the car has accelerated by 4m/s ^2 the first second, 7m/s^2 the second second. Because the car is not speeding up at the same rate, but increasing the rate in which it is speeding up, the car has increasing acceleration. If a car is moving at 10m/s the first second, 18m/s the second, and 25 m/s the third, the car has accelerated by 8m/s^2 the first second ,7m/s^2 the second, and 5m/s^2 the third. Although the car is still increasing its speed, it is increasing its speed slower.
 
The acceleration equation is change in v/time.
The equation for constant acceleration if you want to know how fast something is going is v=at.
The equation for constant acceleration if you want to know how far something is going is d=1/2at^2.
5) Here is a graph that represents constant velocity:
In order to use this graph to solve a problem, the first step is to turn the y=mx equation into words. In this case y=4x would turn into d=4•t. This looks like the formula d=vt. When these two equations are compared, we can see that 4 and v are the only things that are not the same. This means that 4 is the slope. You can now use this information to plug into equations that correspond with the question you are being asked.
Here is a graph that represents constant acceleration:
In this case, because we are dealing with acceleration, time is squared so that we have a straight line. We now go through the same steps as above. We will find that our equation looks like d=1/2at^2.




Thursday, September 4, 2014

Today we Rode Hovercrafts!

Today we rode hovercrafts! Riding on a hovercraft is interesting because once it starts going, it stays at that speed; it never slows down or speeds up unless stopped. It is different than riding on a sled or a skateboard because, unlike a sled or skateboard, it is not slowed down by friction. Riding the hovercraft helped to further understand inertia, net force, and equilibrium.
Inertia can be clearly seen in the hovercraft because when the craft was at rest it stayed in rest and when it was in motion it stayed in motion. What a lazy lout!
We could see net force when the hovercraft was stopped. The force of my classmates stopping the craft was greater than the speed of the hovercraft.
We also learned about equilibrium which happened once the hovercraft had accelerated and started moving because it was not slowing down or speeding up.
Based on this lab, acceleration depends on how hard the hovercraft is pushed and how heavy the person riding it is. The weight of the person riding the craft also makes them harder to stop because mass plays a large roll in inertia. You can find further explanation of this concept in the video I posted recently.
The hovercraft had constant velocity after it had been pushed and before it was stopped. Once it had accelerated, it stayed at the same speed because of Newton's First Law, and the lack of friction.



Here's me on the hovercraft!

Monday, September 1, 2014

Inertia!



Newtons First Law of inertia states that all objects at rest stay at rest and all objects in motion stay in motion unless acted on by an outside force.
This video is a helpful illustration of the law (and a super cool trick that will make you lots of friends). The egg stays in place and falls into the cup because the outside force of the hand hits the plate, not the egg, and there is minimal friction on the egg because of the toilet paper roll. The egg, because it is at rest, stays at rest even when the plate is taken out from underneath it thanks to the law of inertia!