SCIENCE NEWS - WHALE EAR WAX #20

WHALE EAR WAX

Cerumen. It’s a lovely word. Especially considering that it means earwax. And we’re not the only species that produces the stuff. Some whales build up waxes, along with lipids and keratin protein into what’s called earplugs. And researchers now know that examining these plugs tells them about a whale’s lifetime exposure to pollution.
Alternating layers of dark and light in the plugs correlate to seasons of feeding or migration. So the plugs have been used to determine a whale’s age. Think tree rings. 
In the latest study, scientists analyzed an earplug from an endangered blue whale killed by a ship near California. They found that levels of stress hormones doubled over the whale’s life.
They also found evidence that the whale had been exposed to pesticides such as DDT, with the highest levels during the whale’s first six months of life. The whale was likely exposed to the pesticides in its mother’s milk.
They also found a couple of peaks of exposure to mercury. The study is in the Proceedings of the National Academy of Sciences. [Stephen J. Trumble et al., Blue whale earplug reveals lifetime contaminant exposure and hormone profiles]
Future earplugs should offer additional clues about whale lives. So look for researchers to give new attention to leviathan cerumen.
—Cynthia Graber

PHYSICS - MOTION

Energy Around Us

We use the concept of energy to help us describe how and why things behave the way they do. We talk about solar energy, nuclear energy, electrical energy, chemical energy, etc. If you apply a force to an object, you may change its energy. That energy must be used to do work, or accelerate, an object. Energy is called a scalar; there is no direction to energy (as opposed to vectors). We also speak of kinetic energy, potential energy, and energy in springs. Energy is not something you can hold or touch. It is just another means of helping us to understand the world around us. Scientists measure energy in units called joules.

Active Energy vs. Stored Energy

Kinetic and potential energies are found in all objects. If an object is moving, it is said to have kinetic energy (KE). Potential energy (PE) is energy that is "stored" because of the position and/or arrangement of the object. The classic example of potential energy is to pick up a brick. When it's on the ground, the brick had a certain amount of energy. When you pick it up, you apply force and lift the object. You did work. That work added energy to the brick. Once the brick is in a higher/new position, we would say that the increased energy was stored in the brick as PE. Now the brick can do something it couldn't do before; it can fall. And in falling, can exert forces and do work on other objects.

Season of Springs

The study of springs is a whole section of physics. A spring that just sits there doesn't do much. When you push on it, you exert a force and change the arrangement of the coils. That change in the arrangment stores energy in the spring. It now contains energy and can expand and do work on other things. Anything that is elastic (can change its arrangement and then restore itself), such as a rubber band, can store energy in the same way.

A rubber band can be stretched and then it is ready to do something. That stretching involves work and increases the potential energy. You can flatten a solid rubber ball and it will want to bounce back up. You can also pull the drawstring of a bow and the work done stores the energy that can make the arrow go flying. Those are all examples of your putting energy in, and then something happening when the energy comes out.

Gases Storing Energy

Gases? What can they do? Gases are great because they can compress and expand. They act as if they were elastic. If the pressure increases and compresses gas molecules, the amount of stored energy increases. It's similar to a spring, but slightly different. Eventually that energy in the compressed gas can be let out to do something (work).

In your car, there are shock absorbers. Some shocks have compressed gas in the cylinders rather than springs. The energy in those cylinders keeps your car from bouncing too much in potholes. Think about wind. Wind is caused because of pressure differences in the atmosphere. When the wind blows it can do anything - turn windmills, help birds fly, make tornadoes, and do all types of work.

 

Motion

Inertia

• Inertia is the tendency of a stationary object to remain at rest, or the tendency of a moving object to continue at the same speed.
• The heavier the object the greater is the inertia.

          Examples of Inertia

1. When a car brakes suddenly, the driver and passengers tend to keep going in the same direction and at the same speed as before braking. Seat belts are therefore needed to stop them going through the windscreen.

2. It is more difficult to push-start a stationary truck than it is to push a small sedan.
3. It is more difficult to stop a moving truck than it is to stop a small sedan.

PHYSICS - FRICTION

Friction Basics

Friction is a force that holds back the movement of a sliding object. That's it. Friction is just that simple.

You will find friction everywhere that objects come into contact with each other. The force acts in the opposite direction to the way an object wants to slide. If a car needs to stop at a stop sign, it slows because of the friction between the brakes and the wheels. If you run down the sidewalk and stop quickly, you can stop because of the friction between your shoes and the cement.

What happens if you run down the sidewalk and you try to stop on a puddle? Friction is still there, but the liquid makes the surfaces smoother and the friction a lot less. Less friction means it is harder to stop. The low friction thing happens to cars when it rains. That's why there are often so many accidents. Even though the friction of the brakes is still there, the brakes may be wet, and the wheels are not in as much contact with the ground. Cars hydroplane when they go too fast on puddles of water.

Friction and Gases

Friction only happens with solid objects, but you do get resistance to motion in both liquids and gases. This doesn't involve sliding surfaces like friction does, but is instead the kind of resistance you get if you try to push your way through a crowd. It's a colliding situation, not a sliding one. If the gas is air, this is referred to as air resistance.

If you were in the space shuttle and re-entering the atmosphere, the bottom of the shuttle would be getting very hot. The collisions that occur between the molecules of the air being compressed by the shuttle, heat up the air AND the shuttle itself. The temperature on the top of the shuttle is also warm, but nowhere near the temperatures found on the bottom.

Friction and Liquids

Although liquids offer resistance to objects moving through them, they also smooth surfaces and reduce friction. Liquids tend to get thinner (less viscous) as they are heated. Yes, that's like the viscosity of the oil you put in your car. Car engines have a lot of moving parts, and they rub on each other. The rubbing produces friction and the result is heat. When oil is added to a car engine, the oil sticks to surfaces, and helps to decrease the amount of friction and wear on the parts of the engine. An engine that runs hotter requires a more viscous oil in order for it to stick to the surfaces properly.

Measuring Friction

Measures of friction are based on the type of materials that are in contact. Concrete on concrete has a very high coefficient of friction. That coefficient is a measure of how easily one object moves in relationship to another. When you have a high coefficient of friction, you have a lot of friction between the materials. Concrete on concrete has a very high coefficient, and Teflon on most things has a very low coefficient. Teflon is used on surfaces where we don't want things to stick; such as pots and pans.

Scientists have discovered that there is even less friction in your joints than in Teflon! It is one more example at how efficient living organisms can be. 

Friction

• Friction is a force opposing the movement of one surface over another.
• The Magnitude of the Force of Friction depends on the following factors:

1. The roughness of the surfaces (e.g. stepping on banana peel compared with carpet)
2. The force pushing the surfaces together (e.g. A heavy truck's tires compared with a bicycle's tires on the road)
3. Whether the surfaces are moving or stopped

• 3 Types of Friction

1. Static Friction - acting between 2 stationary bodies (e.g. holding a person on a chair)
2. Sliding Friction - acting between surfaces where one is moving (e.g. sliding furniture across the floor, writing with a pencil on paper)
3. Rolling Friction - acting between surfaces of objects where one has a rounded shape (e.g. car tyres on the road, ball bearings); less than sliding friction

• 4 Ways to Reduce Friction

1. Reducing the force pushing both surfaces together
2. Using a lubricant such as oil or water between the surfaces
3. Using ball bearings or rollers between both surfaces
4. Polishing both surfaces