ENERGY

LAWS OF ENERGY
1. Conservation of Energy
2. Law of Entropy
3.Absolute Zero

The first law of thermodynamics says that energy cannot be created or destroyed. Energy can be transformed and transferred.

Many different types of energy exist:

 

• kinetic energy
• gravitational potential energy
• mechanical energy
• chemical energy
• electrical energy
• light energy
• heat energy
• sound energy
• elastic energy
• nuclear energy

 

Kinetic energy describes movement.  

On the other hand, gravitational potential energy is energy due to an object's distance from the ground. This is usually measured when the object is static.  

Gravitational potential energy and kinetic energy combine to form mechanical energy. Mechanical energy is energy produced due to the movement of objects. Mechanical energy assists many machines.Some simple machines aided by mechanical energy are are incline plains and levers. Other machines that make use of mechanical energy are pulleys and screws.

 

Chemical energy is caused by chemical reactions. It  can be called chemical potential energy because there is energy stored in the molecular bonds ready to be used.

 

Electrical energy is caused by charged particles that produce an electrical current. The particles are always moving. On a molecular level this type of energy is kinetic.

 

Light energy is a form of kinetic energy that emits light (visible or non visible to the naked eye).  Sometimes, light energy goes hand in hand with heat energy. 

Heat energy is energy stored in objects above absolute zero. This would comprise of all objects. Heat energy can be either potential or kinetic.When an object is heated, the particles in the object contain more energy and bounce off each other faster. On a molecular level heat energy is kinetic.

 

Sound energy is energy caused by vibrating object. Vibrations are movements of waves in the air. In this sense sound energy is kinetic.

Elastic energy (i.e. spring energy) is potential energy.  It is shown whenever and object is stretched. Springs get either compressed and pulled. Elastics can be stretched out. When someone points a stretched elastic at you , it is an instinct to pull away. This is because people are aware of potential of the elastic to hit you.

 

Nuclear energy energy that is stored in atoms. Nuclear energy is a form of potential energy. Nuclear fusion and nuclear fission are the two types of nuclear energy. Nuclear fusion is a combining of atoms. Nuclear fusion releases a certain amount of energy.  Nuclear fission is the opposite; atoms are split instead.

 

Energy is essential to our lives and well being. Without it, we cannot form chemical bonds in our stomachs and digest the food we eat. Likely without energy we would not exist due to absolute zero. It is important to remember that energy is never lost. It is transformed into different types of energy.

CANNONS

The third class assignment we completed was building a cannon.

This is what we built, kind of. Except that we made it out of popcans.

Cannons are capable of creating a lot of destruction by shooting out cannon balls or simply investing more energy into making much noise. Either way, a real cannon might seem intimidating, which is probably why many ancient battle tactics involved cannons. They had a wide variety of purposes, some of the most common ones involving sinking enemies ships or conquering strongholds.

By analyzing the reason why cannons were so popular we must look at the the way they achieve theirr parabolic motion. Cannons make use of projectile motion. Cannons make use of parabolic motion (due to a vertically shot cannon ball which is brought down by gravity.) Cannons also display the transformation of chemical potential energy into sound energy, kinetic energy, heat energy and work done.

In Kinematics we learned a formula that calculates the range of a projectile.
The velocity in the x-axis is constant because of negligible air resistance. We cannot assume there is no air resistance, however it is low enough not to make a difference in the long run.

The initial height of the projectile is from the ground, thus 0 metres in displacement in the y component. This is not exactly how our cannon operated however, because we raised up the opening where the cannon ball was shot out by about 25 cm.  As well, the optimum angle to shoot the cannon ball at is 45°. This is explained due to the parabolic motion of the cannon ball. The cannon ball will not be shot too low (resulting in a short flying time) nor will it be shot too far up, resulting in a short distance traveled horizontally. If the cannon is shot at a great angle up (e.x. 80°  the range might just be close to 0 metres.) The projectile will be in a parabolic motion, therefore the maximum range might be obtained if the cannon makes a 45° with the ground.

Other factors can contribute to a greater range.  The cannon ball should be as light as possible. The force applied on the cannonball is constant. The mass of the cannon ball is inversely proportional to the acceleration. If the mass of the cannon ball is lighter, a higher acceleration will be achieved. Lastly, the projectile should launched from a longer barrel of the cannon, with more baffles.  more energy will be stored before the cannon is launched. The ethanol will have more surface area to spread over, and therefore it will have the ability to make more connections with air. By increasing the action force acting on the cannon, the reaction force will also increase (equal and opposite reaction force.) This exemplifies Newton's Third Law.

NETON"S THREE LAWS

Newton's Three Laws are:

1. The law of Inertia.  Objects will continue to be in motion or stationary unless it is affected by another force against it.
2. Force=mass . acceleration.  Force is directly proportional to mass times acceleration. Mass and acceleration however share an inverse relationship.
3. For every action force, there is and equal and opposite reaction force. (However it is possible for the reaction force to act in the same direction as the action force. For example if a person with skates is standing constant on ice, and another person skating bumps into the stationary person, the reaction force will send the stationary person in the same direction as the skating person was traveling.)

Four types of problems involving Newton's Three Laws:

1. Equilibrium

Equilibrium is when the object remains static.  These are the assumptions made when solving equilibrium problems:

• there is no friction
• there is no acceleration
• the net force is 0

2. Inclined Planes

There are incline problems can be solved in two ways. (Those involving a static Mk and those involving a  kinetic Mk.) Incline plane problems involves friction because the object is sliding down a slope (hence the name inclined plane). The object has a friction because since the surface is slanted there is a force applied in the x-axis. Friction resists the force. Assumptions to be made when solving incline plane problems are:

For static:

• there is no acceleration
• the positive axes is the direction of acceleration on the surface
• there is no air resistance
• Mu is static if the object is not moving at first
• the normal force is perpendicular to the surface

For kinetic:

• The normal force is perpendicular to the surface
• there is acceleration
• there is no air resistance
• Positive axes are in the direction of acceleration and surface
• Mu is kinetic if the object is moving

When solving incline questions FBDs can be really helpful.  Gravity is always pointing down.  Gravity should be broken down using x and y components.

3. Pulleys

The assumptions when solving pulley problems are:

• the pulley has no friction
• the rope is frictionless
• there is no air resistance
• there are 2 FBDs (one for each load)
• tension for both systems is equal
• Acceleration of the 2 systems is the same
• Positive axes are the direction of the acceleration of each load

4. Trains

Assumptions for train questions:

• there is no air resistance
• there is the same acceleration throughout the whole system
• the y component is in equilibrium (no acceleration) 
• FBDs one for each of the masses
• The cables that connect the masses are weightless
• Positive axis is in the direction of  the acceleration

There are also tension forces connecting the carts. For example the tension force pulling cart 3 forwards is the same as the tension force pulling cart 2 backwards.

Assumptions are very important to include when solving the four types of problems, because it is necessary to specify the conditions concerning a problem in order to find a way to solve it.