Motion and Energy
, all words that are
are rollovers that will display additional text in the form of a pop-up box.
Motion is all around us, and everything, extremely fast or stationary, is in motion.
In the Week 1 lecture we looked
at densities of materials and discovered that that all particles are in motion to one degree or another. Even solids are
made up of particles that are in motion (
vibrational, rotations, and translational) although the motion is too slow for
our eyes to perceive. View the video below for an explanation of the molecular movement within a gas.
The two important aspects of motion are change in position and the passage of time. As such, the motion of an
object is generally described with respect to an outside reference(or
), moving or not.
is the ratio of distance traveled to the time that has elapsed to cover that distance, and it is expressed as speed
= distance/time. In the following illustration, a car moving in a straight line over a distance of 1 mile each minute is
traveling at a rate of 60 mph.
is often used interchangeably with speed; however, because velocity includes both speed and direction,
there is a distinct difference. To affect a change in velocity, the speed, the direction, or both are changed. As shown
below, velocity (v) can be represented as the ratio of the change in distance (d) to the change in time (t) or
The change in velocity and time are combined to create acceleration, or the rate at which motion changes. As shown
below, acceleration is expressed as the
change in velocity
over the elapsed time
is a push or pull that is capable of changing the state of motion of an object. When two forces are parallel in
the same direction, the
is added. When two
are in opposite directions, the
difference between the two forces, and it is in the direction
of the larger force. When two or more forces act in
entirely different directions, a new direction and strength is created. See the figure below.
According to the text, there are four fundamental forces that cannot be explained in terms of any other force. They
gravitational: which are the forces that act between all objects including objects in space
electromagnetic: which are the forces acting between electrically charged particles
weak nuclear: which are the forces involved in certain nuclear reactions
strong nuclear: which are the forces involved in close-range holding of the nucleus together.
These fundamental forces are responsible for everything that happens in the universe including electricity, light,
nuclear energy, and chemical, geological, and astronomical phenomena.