Relative Motion

     All motion is relative.  This means that even though a car moves at 50m/s, if another car is also going 50m/s then relative to each other the cars are really not moving.  However to the ground it is going 50m/s.  But what happens when one car is going 5 m/s but at the same time, a car in the opposite direction is going 10m/s?  This means that when the cars pass each other, relative to each other they are actually seeing the other car go 15m/s in the negative.  This can apply in the real world when we watch baseball.  

      If the pitcher throws the ball at 42m/s and the batter swings his bat at 38m/s then when the bat meets the ball, they are actually meeting at 80m/s.  This is because the ball is going 42m/s in the opposite direction in which the bat is being swung.  This results in an 80m/s collision.  

Projectiles

     A projectile that is launched into the air and is only affected by gravity.  One example of a projectile is a ball much like this.  

     Once this ball is thrown it becomes a projectile.  As soon as it is launched, there is nothing that affects it except for gravity. The motion of the ball is then a parabola because it will go up then gravity will eventually draw it back down.  

     However, the balls acceleration is always zero in the x-axis but its acceleration on the y-azis is 9.8m/s2 down which is the acceleration of gravity.

Vectors

     This past week in physics we learned about vectors.  A vector is a quantity that involves both direction and magnitude.  The way we add vectors is by measuring from tail to tip.  An example of that in a real life situation is in football.  

     When a receiver runs a route, he is running a vector.  If he runs straight 10 yards, then two yards back then the distance that the ball would travel is 8 yards and thats how to add two vectors together with each other.  

Quarter 1 Summary

Quarter 1 Summary

In the first quarter of physics we have learned many things.  The firs thing we have learned was the importance of standards, and more specifically the standards in measurements.  We used an example from old Hawaiian measurements like the pia which is the distance from your extended thumb to your extended pinky.  Another thing we learned was kinematics and motion.  All motion is relative.  So in order to know if something is moving, the question is always, “relative to what?”.  If two cars are going the same speed, they are not moving relative to each other but relative to the road, it is defiantly moving.  Another thing I learned is that the acceleration on Earth is 9.8m/s2.  We also learned the correct way to create a position vs. time graph, a velocity vs. time graph, and acceleration vs. time graph.  We learned how to calculate displacement from a graph and how to sketch the three graphs from information given by the other graphs.  Also we learned about pendulums and periods of time.  We learned how mass and length affected the time it would take the pendulum to swing back and forth five times.  Overall this is the major things we have learned in physics this year.