Happy Valentine's Day--seeing hearts

Here's a really cool video that shows just how much we are pattern seeking animals. We can find hearts anywhere.

You CAN change the world

Never doubt that a small group of thoughtful, committed, citizens can change the world. Indeed, it is the only thing that ever has.

--Margaret Mead

Boy, 7, raises $240,000 for Haitian Relief.

Projectile Motion - 1/19/10

There are multiple concepts that come into consideration when discussing Projectile Motion. Recently, our class (period 1/2) discussed Vertical Velocity (VY), and Horizontal Velocity (VX).

A projectile's horizontal velocity is constant, and has an acceleration of 0. This is due to the fact that there are no substantial forces acting on the object in the horizontal direction. The only horizontal force acting on the object would be air resistance, and in most cases, this force is negligible (i.e. a small steel ball). Because V(sub X) is constant, it's initial velocity is the same as its horizontal velocity at any point in time (unless the object has stopped).

A projectile's vertical velocity has constant acceleration. The earth exerts a gravitational force upon the object that pulls the object towards the earth with a constant acceleration of about 10 meters every second. This is why the object eventually stops moving (in general). The earth's gravitational force brings the object towards it. and the object eventually hits a surface that stops it's motion.

Backyard Ballistics Packet

Here is the reading from backyard ballistics that will tell you how to build a tennis ball morter, catapault, or potato cannon.

Backyard Ballistics

Class on 1/7

today in class we focused a lot on the concept the force of gravity on any two objects will cause them to fall at the same time, despite weight or mass differences.This is because gravity will only exert as much force on and object as it exets on the earth, by having mass orweight. So a light object falling will only exert a small force on the earth, and will only get or require a small reactional gravitational force to make it fall. For a hevy oject, this is true except that it will exert more force on the earth and thus require a greater gravitationl force to be exerted on it. But the objects will fall at the same tie because the gravitatioal forces are different, because the heavier object requires more just to fall at the speed of the light object
Also, we rached the concuion that dropping and object and throwing the same mass object from the same height, without upwards trajectory will result in both object hitting the ground at the same time. Thisis because an objects horizontal motion wil nt affect its vertical motion, so the thrown object will fall at the same time as th oher ball which is dropped, no matter how fast it is going horizontally

Burj Dubai Base Jump

Two basejumpers just set the world record for BASE jumping from the world's tallest building the Burj Khalifa (formerly called the Burj Dubai), from a height of 828 m.

Check out the video below:


Two questions:
1. Why didn't this video take the 13 seconds you calculated take an object to fall to the ground?
2. What was the average velocity of the skydiver? How does this compare to the velocity an object falling only under the influence of gravity would have when it hit the ground?

Wednesday, Jan 6

On Wednesday's Physics class our main or big idea was proving horizontal motion and vertical motion are not related. We concluded that they were not related. We used a cannon on a car to show that when a ball is launched into the air vertically while the car was in motion at a constant velocity horizontally that it will still land in the same place because the ball will still keep its path horizontally after being launched into the air vertically.