Physics and Me: exploring the interactions between energy & matter

“The Elegant Universe” vs. “Who Wrote the Book of Physics?”

kcoghlanadvancedphysics — Mon, 26 Apr 2010 04:53:48 +0000

Although “The Elegant Universe” and “Who Wrote the Book of Physics?” both deal with new thoughts in the realm of Physics, I was surprised at the difference between the two. “The Elegant Universe” presented String Theory as the final step in understanding and uniting the laws of the universe. The ideas of parallel universes and a set of timeless laws were presented without much further questioning. The impression I got was that the show was mostly about Einstein’s quest for unification and his belief that he could approach new problems in old ways, when really he should have looked to quantum physics, which is now on the cusp of unification. However, the ideas presented in “Who Wrote the Book of Physics?” were much different. It is frustrating that the equations physicists rely on are so easily undone; especially when in math we talk about how for a law to be true, it must always be true. I appreciate the fact that these scientists are attempting to bring science back in to the realm of what is observable or falsifiable, even if their own theories may not provide an explanation. The assumption that there are a set of universal, timeless laws in many ways seems like a conclusion before an experiment, and now scientists are forced to create experiments to support their conclusion. This is especially evident in the multiverse theories, in which there isn’t even a need to explain why our universe has the laws it does. And though the idea that physical laws may have changed over time was initially unsettling to me, why not? Science is supposed to not take any assumption for granted and the preeminent theories in physics should not require a leap of faith. After reading, “Who Wrote the Book of Physics?” I almost felt lied to by “The Elegant Universe” because of the seeming certainty with which theories were presented. Coming up with answers to the big questions was never presumed to be easy, and so it’s okay if we can’t figure out the right answers, but I don’t like pretending that we have the answers when we don’t.

Earth’s Precession

kcoghlanadvancedphysics — Thu, 22 Apr 2010 05:04:24 +0000

Both the moon and sun exert a gravitational pull on the earth, which does not have a uniform shape or density, so the gravitational pulls create torque on the earth. Because torque is being applied, the axis of rotation of the earth is shifts, albeit very slowly.

Moment of Inertia

kcoghlanadvancedphysics — Fri, 05 Mar 2010 05:58:20 +0000

The Moment of Inertia is the measure of how much a body opposes change in its rate of rotation due to spinning, this measure is based on the mass of the object and radius from the axis of rotation. The moment of inertia is greater the farther out the mass is from the center because more force is needed to change its rate of rotation.

Energy: Heat and Light

kcoghlanadvancedphysics — Tue, 16 Feb 2010 05:44:11 +0000

Greenhouse gases absorb infrared radiation and trap its heat. “Trapping heat” is probably through conduction, in which the molecules vibrate more rapidly and collide with one another, which transfers heat. Heat itself is a type of energy that describes the atomic and molecular motions of a substance. Light is made up of wavelengths with different amounts of energy. Molecules seem to “interact” with energy through their motion—how much and how quickly they move and vibrate.

Kinetic Energy vs. Momentum

kcoghlanadvancedphysics — Wed, 10 Feb 2010 02:53:14 +0000

Momentum is a vector that provides the impulse whereas kinetic energy is a scalar quantity that does the work on an object; in a collision, momentum must be conserved, but whether kinetic energy is or not characterizes the collision as either elastic or inelastic.

Asteroid on the Edge of Infinity

kcoghlanadvancedphysics — Thu, 21 Jan 2010 06:51:47 +0000

These equations (7.18/19) would not help us with the problem of the asteroid at the edge of the universe because we would need to have a value for the upward displacement (the distance between the asteroid and earth) as well as the upward applied force (the force gravity exerts on the earth). If the asteroid is “infinity” away from the earth, the net work is going to being infinity, which could mean that the asteroid would have infinite potential energy, but this doesn’t help us much.

Impulse and Egg Drops

kcoghlanadvancedphysics — Wed, 13 Jan 2010 05:48:03 +0000

The purpose of the egg drop is to have the egg not break. To have this happen, we want to create the least amount of force on the egg. Because the Impulse is the same as the change in momentum, it is constant, so to have the least amount of force, the change in time should be made greater. This means that we want to slow down how quickly the egg is stopped, which means there should be something to ‘soften’ the fall.

Mechanical Energy vs. Non-Mechanical Energy

kcoghlanadvancedphysics — Mon, 11 Jan 2010 03:48:17 +0000

The mechanical energy of a system is the sum of both the kinetic energy and potential energy of the system. In other words, it is energy due to position or movement.
Non-mechanical energy is anything that does not fit this description. This type of energy takes place on the atomic level, and it could be light energy, chemical energy, electrical energy, or sound, among others.

Circular Motion

kcoghlanadvancedphysics — Tue, 24 Nov 2009 16:32:36 +0000

6.) No, because for the astronaut to be in orbit, the gravitational force must be acting on him. The astronaut will still have mass because it is an intrinsic property and there would have to be acceleration if he is being acted on by the centripetal force keeping him in orbit, so because F=ma, the weight force will not be zero, meaning that the astronaut will not be weightless.
7.) This imitation of gravity could work because if people were inside, the centripetal force would be pushing them outward, towards the walls of the cylinder. This ‘pushing out’ could be like the ‘pulling down’ of gravity, at least in theory. However, it would not work for the people to live on the outside of the cylinder because, unlike the rubber stopper attached to the string, they would not be attached to the rotating cylinder, so they would continue at a constant velocity in the direction tangent to the cylinder at that point.

Newton’s Laws Questions

kcoghlanadvancedphysics — Mon, 02 Nov 2009 04:43:09 +0000

1.) The gravitational force acts on the ball, but the ‘normal force’ created by the hand is the reaction force to this and keeps the ball from falling to the ground. If the ball is dropped, the earth’s gravity is acting on the ball, and the reaction force is the ball’s gravity acting on the earth. However, the mass of the ball is so small compared to the earth, that this has basically no effect.
5.) To get the water off your hands, you could shake them. Doing so exemplifies Newton’s First Law of Motion, which, in a very simplified form, is that an object in motion tends to stay in motion and an object at rest tends to stay at rest. The water moves as your hands move, but when you stop your hands, the water continues moving and flies off your hand.
10.) If the “force of the throw” is greater than the force of gravity, then the ball will move upwards. Technically, the “force of throw” can be equal to the force of gravity, but then there would be no throw; the ball would just be resting in the child’s hand, neither moving up nor down. The “force of the throw” is the speed at which the child’s hand is moving. The ball moves away from the child’s hand because of its’ inertia; the movement of the hand provides the force to propel the ball in a direction and even when the hand stops moving, the ball continues, but is eventually brought back down because gravity continues to act on the ball.