Hard Solutions / Coastal Construction

Swash Bucklers

Start here for animation on Coastal Changes

We are now experimenting on how human interaction can affect natural coastal changes



Several engineering solutions are used for coastal protection and beach restoration. In the past, construction of hard structures, hard solutions such as groins and sea walls, jettys and breakwaters have been used with varying degrees of success. Some solutions have been successful, some require expensive ongoing maintenance and others have caused even more problems. Another method of coastal protection is to artificially nourish the beaches by transporting sand from another location to restore a beach. Once again, this method has varying levels of success.

Students are attempting to answer "Hard Solution" questions regarding beach and coastal erosion. They "wonder" WHAT and HOW "hard solutions" to beach erosion are supposed to work.

Developing testable predictions ...... defining independent and dependent variables...

IF IV

Then DV

Students developed a myriad of possible solutions...




If you increase the resistance to beach swash, then the landward beach erosion will...... (hmmmmmmm?... increase? ...decrease?... stay the same?)


Groins and Longshore Drift

Groins, usually made of timber, rock or concrete, are built perpendicular to a beach and into the water to trap sand. On beaches where waves arrive at right angles to the shore, a series of groins can trap sand, creating a series of small beaches







On beaches where waves arrive at an angle to the shore and the beach is affected by longshore drifting, a different situation arises. As the water and sand move by, the first groin will trap sand meanwhile starving the beach of sand (and other groin) further along the shore. Groins can be designed to allow some sand to spill around the structure and minimize downstream erosion.

Groins are not successful in all circumstances contributing to further erosion. A careful analysis of wave approach and currents should precede any decision to install a groin, and the structures should be carefully designed for the specific location.






Seawalls



Seawalls may be constructed of timber, rock, steel or concrete and are placed at the back of a beach. Although seawalls can protect the land directly behind, they can also accelerate erosion at the end of the wall and/or cause erosion of the beach in front of the seawall. When waves hit the wall and retreat, the wave action scours sand from the beach back into the water. Ultimately, the beach becomes lower and flatter, creating a condition where waves become larger, which increases the scouring action and the beach is eventually lost.
Artificial beach nourishment (replenishment) is the depositing of sand from elsewhere to replenish eroded beaches. Sand may be trucked in or dredged and pumped from offshore. But it is not as easy as it sounds. The nourishing sand must be as coarse as the sand that is currently on the beach. If the nourishing sand is of a finer grain, the sand will be easily swept away by normal wave action. On beaches where sand has been lost through longshore drifting it is likely that nourishing sand will also be lost. Sometimes in this scenario, groins are constructed to trap drifting sand.

It is important to remember that coastal erosion is a natural process and does not always have a negative outcome. It is the natural erosion process which gets sand on beaches in the first place, but if interference occurs with natural erosion and deposition patterns, undesired outcomes requiring further action can occur.


So what is the solution? Or has nature found its own solutions and we have just ignored them?


What do you think?

Who has the Momentum?

Momentum summary. Use this as a supplement to your textbooks.

Momentum

The sports announcer says, "Going into the all-star break, the Chicago White Sox have the momentum." The headlines declare "Chicago Bulls Gaining Momentum." The coach pumps up his team at half-time, saying "You have the momentum; the critical need is that you use that momentum and bury them in this third quarter."

Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion (on the move) then it has momentum.

Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

Momentum = mass • velocity

In physics, the symbol for the quantity momentum is the lower case "p". Thus, the above equation can be rewritten as

p = m • v

where m is the mass and v is the velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity.

The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kg•m/s. While the kg•m/s is the standard metric unit of momentum, there are a variety of other units that are acceptable (though not conventional) units of momentum. Examples include kg•mi/hr, kg•km/hr, and g•cm/s. In each of these examples, a mass unit is multiplied by a velocity unit to provide a momentum unit. This is consistent with the equation for momentum.

Momentum is a vector quantity. As discussed in an earlier unit, a vector quantity is a quantity that is fully described by both magnitude and direction. To fully describe the momentum of a 5-kg bowling ball moving westward at 2 m/s, you must include information about both the magnitude and the direction of the bowling ball. It is not enough to say that the ball has 10 kg•m/s of momentum; the momentum of the ball is not fully described until information about its direction is given. The direction of the momentum vector is the same as the direction of the velocity of the ball. In a previous unit, it was said that the direction of the velocity vector is the same as the direction that an object is moving. If the bowling ball is moving westward, then its momentum can be fully described by saying that it is 10 kg•m/s, westward. As a vector quantity, the momentum of an object is fully described by both magnitude and direction.

From the definition of momentum, it becomes obvious that an object has a large momentum if either its mass or its velocity is large. Both variables are of equal importance in determining the momentum of an object. Consider a Mack truck and a roller skate moving down the street at the same speed. The considerably greater mass of the Mack truck gives it a considerably greater momentum. Yet if the Mack truck were at rest, then the momentum of the least massive roller skate would be the greatest. The momentum of any object that is at rest is 0. Objects at rest do not have momentum - they do not have any "mass in motion." Both variables - mass and velocity - are important in comparing the momentum of two objects.

The momentum equation can help us to think about how a change in one of the two variables might affect the momentum of an object. Consider a 0.5-kg physics cart loaded with one 0.5-kg brick and moving with a speed of 2.0 m/s. The total mass of loaded cart is 1.0 kg and its momentum is 2.0 kg•m/s. If the cart was instead loaded with three 0.5-kg bricks, then the total mass of the loaded cart would be 2.0 kg and its momentum would be 4.0 kg•m/s. A doubling of the mass results in a doubling of the momentum.

Similarly, if the 2.0-kg cart had a velocity of 8.0 m/s (instead of 2.0 m/s), then the cart would have a momentum of 16.0 kg•m/s (instead of 4.0 kg•m/s). A quadrupling in velocity results in a quadrupling of the momentum. These two examples illustrate how the equation p = m•v serves as a "guide to thinking" and not merely a "plug-and-chug recipe for algebraic problem-solving."

1996-2011 The Physics Classroom

Do not Hesitate to use The Physics Classroom their help is greatly appreciated
and they provide great reviews and different perspectives to help you better understand the principles and calculations in Physical Science.

More examples to come... Does this help?

This is a GREAT SITE for practicing Momentum calculation problems..

Did I say that loud enough...

This is a Great Site !!!!

an excerpt :

Steps for Solving Momentum Problems

As in the procedure for solving other force problems, calculating momentum is a step by step process. We will use a problem to work through the steps.

Problem: Calculate the momentum of a 11.35kg wagon rolling down a hill at 12m/s.

Step 1 : Write down the equation needed for solving momentum.

p = mv

Step 2: Insert all known measurements into the formula.

p = (11.35kg) (12m/s)


Step 3: Solve. Carefully enter all numerical values into your calculator.

p = 136.2 kg x m/s down the hill

• Check your work and make sure that all numbers have a SI unit label and that you have the correct SI unit for momentum.
• Don't forget the direction in your answer label! The velocity is down the hill, so the momentum will be the same.
• It is a good idea to always double check your answers because it is very easy to hit the wrong button on your calculator!

Go get some momentum formula experience! Do the practice problems.

Help solving one step formula problems click here


Practice Momentum Problems at the bottom of the page.

It's Elementary my dear Watson

Elements

(this site will be under continual construction)







A Visual Periodic Table


A very complete resource for the Periodic Table from WebElements

An ionic bond (or electrovalent bond) is a type of chemical bond that can often form between metal and non-metal ions (or polyatomic ions such as ammonium) through electrostatic attraction. In short, it is a bond formed by the attraction between two oppositely charged ions.

The metal donates one or more electrons, forming a positively charged ion or cation with a stable electron configuration. These electrons then enter the non metal, causing it to form a negatively charged ion or anion which also has a stable electron configuration. The electrostatic attraction between the oppositely charged ions causes them to come together and form a bond.

Remember Robin Hood? The Sheriff of Nottingham?

Here you find a video about every element on the periodic table, COOL!








Follow the amazing connection of THE ELEMENTS AND LIFE.

(thanks to an excerpt from Media Wiley http://media.wiley.com/product_data/excerpt/52/35273206/3527320652.pdf)


Yes, some of the connections seem quite complex, but while you are reading take note of the simplicity of whole numbers that literally bind life together -





... a seeming Infinite Diversity in Infinite Combinations from so few (27) essential elements...
(don't forget to check for your element)

Thank goodness you had Life Science last year... and now , 4...5...6... almost a little spooky!

The last paragraph is about you. No, seriously, it really is about you!


A simple Practice Quiz.... Chem For Kids

A different perhaps more challenging Quiz ... Proton Don

And now an advanced (7th) Grade Quiz ... Quia Quiz

So, what do you think?
How did you do?

Find anything out about your element?