Chapter2Section1

Chapter 2 Section 1

__**Learning Outcomes**__

 * Describe**: Galileo's law of inertia
 * Apply**: Newton's first law of motion
 * Recognize**: inertia mass as a physical property of matter
 * Use** **example to demonstrate**: that the speed is always relative to some other object
 * Explain**: that the speed of an object depends on the reference frame from which it is being observed

__**What Do You See?**__
toc
 * mouse and ladybug are trying to kick the ball, but it is not moving because of inertia
 * kid running to kick the ball so it goes over the net
 * all different examples of inertia
 * standing still kid made the ball not go very far
 * wind blowing on the tree in the background

__**What Do You Think?**__
Every sport includes moving objects or people or both. That is what makes sports entertaining. -physics determines motion so it relates to sports -friction: is a force that resists the object from moving across a surface -an hockey puck slid across grass will not slide (lots of friction) and if it is slid on ice it will coast along (very little friction) -smoothing the ice reduces the amount of friction -the force acts upon it to start its moving and it does not stop right away because the ball is a smooth surface so there is nothing weighing it down -an object in motion wants to stay in motion
 * How do figure skaters keep moving across the ice at high speeds for long times while seeming to expend no effort?
 * Why does a soccer ball continue to roll across the field after it has been kicked?-

__**Homework 12/7/11**__
__**http://nvonews.com/2011/12/07/new-planet-kepler-22b-600-light-years-away-can-you-reach-there/**__
 * New Planet Kepler-22b 600 light years away: Can you reach there?**
 * this new planet was discovered by NASA's Kepler mission
 * this planet is suited for human life and is about 70 degrees
 * it is thought to be in the habitable zone, which means that it suggests there is water and other necessary resources to support life
 * it is 600 light years away (a newborn baby would not reach this planet alive)
 * **light year:** measures distance in space (this planet is about 10 trillion kilometers or 6 trillion miles away)
 * with the best spaceship NASA has right now it would take about 1200 years to get there
 * the surface of this planet is still unknown
 * **NASA's Kepler mission**: launched a mission that will detect each time that a planet blocks a start because it is orbiting around its parent star (this is called a periodic dimming which allows the size and orbit to be determined
 * this mission has found over 1200 planets, but this is the first in the planet seems to be habitable (photometer: specialized one-meter in diameter telescopes are being used to measure any small changes in brightness occurring on this planet known as transits)

__**Investigate**__

 * When a ball is released to roll down a track and up the opposite side of the track, how does the vertical height that the ball reaches on the opposite side of the track relate to the vertical height from which the ball is released?

-the slope should be steep, 1-m track and the ends should be elevated 30 cm a. Place the ball on the left-hand section of the track. Measure and record the vertical height (not the distance along the track) from which th eball will be released. This shoudl be about halfway up the track. This is the starting height b. Release the ball and mark where it reaches the highest point on the opposite track. This is the recovered height. Measure and record the vertical height of this mark. Concentrate on comparing the vertical height of the ball's release position to the vertical height of the position where the ball stops before rolling back. a.) starting point: 30 cm ending point: 29 1/2 cm

2. Change the recovered-height section of track so that its slope is less steep, but its end is still as high as the height from which you release the ball. The track should be arranged approximately as shown in the next diagram, with a medium steep up-slope. starting point: 20 cm ending point: 20 cm random error, about the same height as the starting point
 * I think that it will reach about a 1/2 cm lower than the staring point.

3. Now try it for real. Mark on the track where the ball reaches its highest point. a. How close was your prediction to the actual outcome? Why do you think your prediction was "close" or "way off"? -My prediction was close and would probably been much closer if it was not for the random error that occurred when measuring the ending point. b. Measure the vertical height where the ball stopped. Write a sentence that fully describes the movement of the ball in terms of its starting and recovered vertical heights. The ball was released at 20cm with the ending height of 20cm. Both with some uncertainty.

5. IMagine what would happen if you changed the right-hand section of the track so that it would be horizontal (zero slope), as shown below. a. No matter how far along the horizontal track the ball rolls, would it ever recover its starting height? No, because it is losing its energy cause there is friction slowing it down. b. How far do you think the ball would roll? Friction or something in its way would eventually stop it. c. What would keep the ball rolling on a horizontal track, like the one shown in the diagram above? If there was no friction because nothing would be taking away its energy to slow it down. (no forces acting on it: Newton's First Law) No friction or forces it could roll indefinitely.

__**Do Now: 12/9/11**__
1. If a skateboarder starts at the top of a 4 meter tall half pipe and travels around to the other side, how high off the ground will he reach if you ignore friction? (can not get even more energy then it began with) -if there is friction it would reach a little less than 4 meters (if no gravity and no friction you would only stay in contact with the half pipe until it ends and you would keep going off the end
 * 4 meter

2. If friction is not ignored, how high will he reach? If friction is ignored then it will reach the same height as the starting height

3. How does this scenario illustrate Newton's 1st Law of Motion?
 * An object will stay in motion at a constant speed unless a force acts upon it, just like the skateboarder who starts at a certain speed and continues in that speed.

__**Physics Talk**__




Running Starts: v(javalin)=v(hand)+v(elbow)+v(shoulder)=v(body)

Frame of Reference: the way you look at a speed, dependent on your visual perception

__**Checking Up**__
1. What is inertia? -Inertia is the tendency of an object to remain at rest or in motion in a straight line.

2. Describe Newton's first law of motion? -In the absence of an unbalanced force, an object at rest remains at rest, and an object already in motion remains in motion with constant speed in a straight-line path.

3. What needs to act on an object to stop it from moving at a constant speed? -A force like friction or gravity.

4. In the real world, a rolling ball does not roll forever. What stops the motion of the ball? -Friction, gravity, or another object will stop the motion of the rolling ball.

5. Given two different-size masses moving at the same speed, which mass will have the greater inertia? -The object with the larger mass will have the greater inertia because the larger it is the harder it is to stop from moving or to make it move.

6. You throw a ball in a moving train. Why is it important to establish a frame of reference when describing the speed of the ball? -If you do not give a frame of reference then your answer will be misleading because now your speed can be in reference to the ground or to the train.