Wednesday, March 19, 2008

DPS906 Lecture March 19

displacement = velocity * time (if there is no acceleration over time)
displacement = velocity * time + 1/2accel*time*time

what we are missing is a justification for the velocity. We do not have a reason for velocity right now.

Causes of Motion

Mass - amount of matter OR amount of resistance to change in motion.
- stationary things are in motion, with a velocity of 0.
Mass is a scalar... no direction
Additive... if a thing is made out of different parts, you can simply add them together to get the mass of the whole thing.

Centroid is the geometric center of a 3d object. The centroid is the center of mass for objects with uniform density.

For objects that do not have uniform density the center of mass must be calculated.

To find the center of mass for a non-uniform dense object...
- pick some point as a reference (it doesn't matter where),
- From that reference point, create vectors to each of the centers of mass of the components.
- center of mass of whole = (m1*v1 + m2v2) / m1+m2

Newtons Laws
1) Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
2) The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.
3) For every action there is an equal and opposite reaction.

force = mass * acceleration something

No comments: