In Class with Dr. Prince: March 2013

Sunday, March 31, 2013

Newton's Laws of Motion

You can predict, calculate, and describe motion if you understand Newton's Laws.

Motion Laws

2nd - Force is equal to the mass and the acceleration of an object. What pictures can you create to make sense of this law?

3rd - For every action, there is an equal and opposite reaction.What pictures can you create to make sense of this law?

Look at what Advance Science students worked on!

Student Work on Motion and Forces

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Sunday, March 24, 2013

Gravity, Air Resistance, and Motion Laws

Unit Vocab Flashcards

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Gravity

Gravity is the force that pulls two objects together. If that's so, why is it I am not more attracted to my bed when it's time to get up in the morning? Well, mass has a great deal to do with gravity. The more mass an object has, the more gravitational pull. Unfortunately, since my bed doesn't have as much mass as the Earth, I have a much greater chance of being pulled to the Earth, then being pulled to my bed. Let's consider the example provided on the anchor chart in class. We have two kids sitting next to one another in the grass. Because the gravitational pull is weaker between them then each to the Earth, they will be more attracted to the Earth than one another because of the difference in the amount of their masses and the mass of the Earth.

Now there is another event that can influence the gravitational pull between objects. The closer one object is to the next object, the greater the gravitational pull. The further away one object is from another one then the lesser the gravitational pull is between the objects. Again, let's go back to the image on the anchor chart in class. The gravitational pull between you and Earth is much greater than the gravitational pull between you and Venus. The distance between you and Venus is much greater than the distance between you and Earth.

Air Resistance

Air resistance is the opposing force between forward movement and the air. Air is a gas and therefore it makes air resistance one example of fluid friction. Remember, fluid friction occurs between a gas or liquid and an object that is surrounded by the air or liquid. Fluid friction resists the movement of a solid object through a fluid. Air resistance is an upward force. Think about the picture in the textbook with the leaf and acorn. These objects are falling from the tree. Since falling implies a downward motion the opposing force would be exerted in an upward motion. Both objects don't fall at the same rate because of their different surface areas. The greater the surface area = the greater the air resistance; the lower the surface area = the lesser the air resistance. How does the weight and gravitational pull influence the falling of these two objects?

Friction

There are four types of friction as we learned and reviewed in class last week. Read more about friction here and watch this video here. Friction is helpful because it helps to create warmth when two surfaces rub against one another. Friction slows down motion with is helpful especially when a traffic light is going from yellow to red. Friction can be an obstacle too! If there is too much friction it makes it hard for an object to move, it wears down objects. Too little friction can be an issue too! Recently, I purchased a new pair of heels. After I put them on and walked on a particular surface I almost slipped! Why? Well, there was not enough friction between the bottom of my shoe and the surface of the floor. Friction is increased by the roughness of the surface. Smoother surfaces have a lower frictional force, while a rough surface, like the road, creates more friction. Check out this website of 25 examples of friction and determine how friction is either harmful, helpful, or both for each one.

Motion Laws

1st - An object in motion stays in motion. An object at rest remains at rest. Motion only changes when another force is exerted upon the object. What pictures can you create to make sense of this law?

2nd - Force is equal to the mass and the acceleration of an object. What pictures can you create to make sense of this law?

3rd - For every action, there is an equal and opposite reaction.What pictures can you create to make sense of this law?

Student Work on Motion and Forces

Created with Padlet

Monday, March 18, 2013

Parent Night Reminder

Sunday, March 17, 2013

A Deeper Look At Different Forces

How do you know if an object is moving?

The quickest and easiest way to determine if an object is in motion is to decide whether its position has changed.

What causes a change in motion?

Unbalanced forces do! When the forces around an object are equal, we call it balanced force. This means that the object is not moving. However, if one force becomes greater than another than we call it an unbalanced force. This unbalanced force causes the object to move in the direction of the greater force.

So are there other forces acting on the mouse? Yes there are! Let's go through them all first.
Applied force (FA) --> the force being applied to an object
Gravitational force (FG) --> the force gravity exerts on an object
Normal force (FN) --> the force that is equal and opposite of the gravitational force; supports the object that it is in contact with
Frictional force (FF) --> the opposing force

What is the role of inertia in all of this?

Inertia is an objects ability to resist change in its motion. The more mass an object has the greater inertia it has. In other words, if I try to push the mouse on a mouse pad it will move without too much effort because it has little inertia. A motionless elephant on the other hand has a greater mass and that means its inertia is greater too. It will be much harder to move this elephant because of its inertia (resistance to change its motion--remaining still).

Newton's 1st Law (Law of Inertia) - an object in motion remains in motion and an object at rest remains at rest until a force acts upon it.

This simply means that an object that is moving will keep moving unless a force stops it and an object that is not moving will begin to move once an applied force changes its position.

This week we will spend some time just understanding these forces. Don't forget to bring your critical eye to the classroom!

Monday, March 11, 2013

Monday's math problems

Here you go

Sunday, March 10, 2013

Forces All Around

Standards:
S8P3a. Determine the relationship between velocity and acceleration.
S8P3b. Demonstrate the effect of balanced and unbalanced forces on an object in terms of gravity, inertia, and friction.

Goal:
Explain the relationship between force, mass, and the motion of objects.

Objectives:
SWBAT explain the relationship between velocity and acceleration.
SWBAT create original examples of balanced and unbalanced forces in their daily lives.
SWBAT graph velocity and acceleration and find the slope of the line.

Big Ideas:
1. An object in motion changes position.
2. Speed measures how fast an object's position changes.
3. Acceleration measures how fast an object's velocity (speed) changes.
4. Forces change motion.
5. The force and mass of objects determine their acceleration.
6. Gravity is a force exerted by the mass of and distance between objects.
7. Friction is a force that opposes motion.

Vocabulary:
motion, reference point, speed, velocity, acceleration, force, net force, inertia, balanced force, unbalanced force, gravity, friction, mass, weight, slope

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Friday, March 8, 2013

Weekend Work

Here are the pictures of today's math problems. Copy the problem. Make your T-chart. On the left side write the correct formula, plug in the values, and solve. On the right side graph the slope of the line using the speed. No graph is necessary for items 4, 6, 7, and 8. Will your class be the next to make the 85% challenge? Stay tuned on Monday to find out. Have a great weekend.

Sunday, March 3, 2013

May the FORCES be with You!

B.I.1: An object in motion changes position.

I know an object was in motion if the distance between it and other object changes. The other object that I am using to determine if motion occurred is called a reference point. Look at my diagrams below.

In the first picture, the beach ball is far away from the tree. In the second picture, the beach ball is closer to the tree. The tree is my reference point. I use the tree to help me determine if the object--the beach ball--moved. I can also measure the distance between the point A and point B to also confirm my observations. The SI unit for measuring length is meters.

B.I.2: Speed measures how fast an object's position changes.

Do you remember learning about slope? Well, there is a relationship between slope and an object's speed: they are one in the same. Slope measures the steepness of a line and you can find it by the ratio of the rise and the run.

To graph the speed of an object, you use a distance-time graph. This graph is similar to the one used in calculating the slope of a line. In this case, the x-axis (the independent variable) is always time. The y-axis (the dependent variable) is distance. Remember to label the axes accurately because time never depends of the distance traveled. The distance traveled depends on the amount of time in which to travel that distance.

Let's look at a few speed graphs.

To calculate the slope of a line, you find the change of y over the change of x. The rise of a line is along the y-axis and the run moves along the x-axis. The rise of the line is 1 and the run is 2. The slope, which is m, equals 1/2. Since the slope is 1/2, the speed of the object is 1/2 meters per second. This means that there is a constant rate of change. For every second, the object is moving 1/2 meter.

Now look at this graph. Can you see the connection between the slope and the speed? For every second, the object is moving 3 meters. Now look at the next graph.

Do you notice something in this graph about the steepness of each line? The steeper the slope (the higher the line), the faster the object is traveling. There is clearly a relationship between the steepness and speed of a line. Now what about the next example?

What do you think a horizontal line or zero slope means? Let's start with the time. As the line moves fro the left to the right, it appears to be increasing. What about the distance traveled by the object. It looks like this object has been in the same position (3 m) for some time. Remember time is also going whether the object moves or not. This object has a slope and speed of 0 m/s, which means it is simply not moving at all.

B.I.3: Acceleration measures how fast an object's velocity changes.

How many ways can an object accelerate? Is 1 your guess? I am sure you are thinking of acceleration in terms of an object speeding up. There are actually to other ways for an object to accelerate: by slowing down (negative acceleration) or change direction! Yep, that's right. So that's a total of three ways for an object to accelerate.

An object speeding up (positive acceleration): If an object is moving faster than the speed at which is first started moving, you will see a positive acceleration. So let's say that an object had an initial speed of 1 m/s and had a final speed of 7 m/s over a period of 3 seconds. Here is how that is calculated:

An object slowing down (negative acceleration): If an object is moving at a slower speed than which it started, you will see a negative acceleration. For example, if an object has an initial velocity of 10 m/s and then has a final velocity of 0 m/s, over a period of 20 seconds, it would look like this:

An object changing direction: Velocity is defined as the speed in a given direction. So whereas an object's speed might be 3 m/s, its velocity would be 3 m/s going North (or whatever direction).

Need more on calculating acceleration? Watch this video that shows how to calculate acceleration.