Physics Oh Yeah!

[heffphysics-blog]

December 21st

Today was our last Physics class of 2011.  We further discussed the relationship between Actual Mechanical Advantage (AMA) and Ideal Mechanical Advantage (IMA).  I learned that no system will ever have 100% efficiency due to real world losses, such as friction.  We also went over our homework.  One problem I found interesting was the one about the pyramids.  It was interesting to see how physics helped people thousands of years to build amazing structures, even with their limited technology.  I think we don't take into account how much physics impacts our lives.

[ajohn794-deactivated20120725]

Machines - December 19, 2011

Today in class we discussed how exactly “machines” get involved in physics.  Basically machines are used to increased a force and change the direction of a force.  The attached picture shows a young child using a complex pulley system to pull up a small bucket.  The amount of work put into the pulley is equal to the amount of work put out of the pulley.  Other examples of machines in physics would be levers or inclines. 

[michaelsantini-blog]

That kid looks like he is having a lot of trouble pulling up the bucket of whatever. I thought that the more pulleys you have (and he has a lot) the easier it is to lift the mass at the other end of the string. This kid must be really frail. 

[heffphysics-blog]

 He does seem quite frail. Perhaps he is in need of more pulleys.

[heffphysics-blog]

Today in class we continued our discussion on machines.  I learned there are three simple types of common machines.  They are levers, pulleys, and inclines.  No machine has 100% efficiency.  I learned some formulas for efficiency. 

eff. = (useful work output)/(total work input)

eff. = (actual mechanical advantage)/(theoretical mechanical advantage)

[heffphysics-blog]

Monday December 19th

Today we began discussing machines.  I learned a machine is a device for used to either increase a force or change the direction of the force.  I learned that the work input = the work output.  So if Win = Wout that means Fd=Fd.

[heffphysics-blog]

Friday December 16th

On Friday we had a lab.  We tried to measure the efficiency of different pulley systems.  I learned some new terms such as:

Effort - the force supplied by the person using the machine

Resistance - the force which the machine applies to the load

Effort Distance - the distance which the person using the machine moves the machine

Resistance Distance - the distance which the machine moves the load

I also learned some new relationships:

Actual Mechanical Advantage (AMA) = Resistance/Effort

Ideal Mechanical Advantage (IMA) = (Effort Distance)/(Resistance Distance)

Efficiency = (AMA/IMA)*(100%)

[rkuz-blog]

This week we learned about Potential energy. Potential energy is the energy of position and it refers to the relative position of two objects. When an object has potential energy, it has this energy because it is in a stored state and has the potential of doing work. Gravitational potential energy is the work that was required to elevate the object against gravity. The equation used to calculate gravitational potential energy is PEg=W=Fd or PEg=mgh. Gravitational potential energy depends on two factors. These two factors are the weight of the object and the height of its elevated position.

[heffphysics-blog]

 Nice picture relating potential energy to everyday activities.

[heffphysics-blog]

Thursday December 15

Today in class we began learning about the conservation of energy.  I learned that when energy changes from one form to another there is no net loss or gain of energy.  I also learned that energy cannot be created or destroyed, it can only be transformed into different forms.  This was familiar to me from chemistry and doing experiments with closed systems.  We were given some helpful formulas for energy that we used in solving a problem involving a roller coaster. 

E= KE + PE        KE (before) + PE (before) = KE (after) + PE (after)

[heffphysics-blog]

Wednesday December 14th

Today we continued reviewing KE and PE and went over the workbook problems.  It was interesting to see how all the equations we have learned tie together and can be used and substituted for one another.  It was cool to learn how objects PEs can be related through the forumula PE=mgh, and how a 2kg object 10m from the ground has the same potential energy as a 10kg object 2m from the ground.

[heffphysics-blog]

Monday December 12th

Today we review Kinetic Energy and did some pratice problems involving it.  We were also introduced to Potential Energy.  I learn that potential energy is the energy of position and it involves the relative position of 2 objects.  I learned PEg is the work that is required to elevate the object against gravity (PEg=mgh) where h is the distance above the reference point.  While PEsp is the work that is required to displace a spring a given distance (PEsp = 1/2kx^2) where k is the spring constant (F=-kx) and x is the displacement.

[rkuz-blog]

This week we talked about work. Work is the product of an object and the distance it is moved, therefore if work occurs, the object must move (W=FD). If there is no movement there is no work. There are also different types of work. One type is work done against another force, and the other is work done to change the velocity of something.

[heffphysics-blog]

 What example of how work is done!

[heffphysics-blog]

This week in class we have been talking about work and power.  Work is equal to force times distance.  Power is equal to the work divided by time.  Today we also began learning about kinetic energy.  KE=1/2mv^2. 

[heffphysics-blog]

Tuesday Posting

Tuesday in class we reviewed for our test and began discussing work and power.

[heffphysics-blog]

December 5th

Today I learned about work and power.  Work is equal to the force times the distance

W=Fd.   And Power is equal to the work divided by the time.  P=W/t.  We also had a lab today.  For the lab we calculated our times running up a flight of stairs.  Using our results we calculated many other factors such as our horsepowers, watts, and we also measured our weight in Newtons.

[rkuz-blog]

This week we talked about the 2 types of collision, elastic and inelastic. Elastic collisions occurs when 2 objects collide and bounce apart with no energy loss. KEi=KEf. Inelastic collisions occur when 2 objects collide and some mechanical energy is transformed into heat. KEi > KEf

[heffphysics-blog]

 Nice video!

[heffphysics-blog]

 On Friday we went to West Point.  The cannons there reminded me of how momentum is conserved.  Before the cannon is shot there is no movement, but when it is shot the cannon ball comes out one end.  To conserve momentum the cannon experiences recoil, and total momentum after it is shot equals the total momentum before.

[heffphysics-blog]

Elastic and Inelastic Collisions

This past week we have been talking about elastic and inelastic collisions.  Elastic Collisions involve no loss of energy, while inelastic collisions do. 

[heffphysics-blog]

Today I learned about impulse.  Impulse is equal to the change in momentum.  Impulse plays a role in our everyday lives as well as in sports, such as soccer shown here in this video.