P201 Menu


October 20, 1998


Let's first review kinematics then look at the posted sample test then at keys to the test.


V = DX/Dt and a = DV/Dt


X = Position Along the Path of Motion.

V = Velocity Along the Path of Motion.

a = Acceleration

apath changes magnitude of V.... slope of graph of v vs t.

aperp changes direction of V.... aperp = V^2 / R


Ways to picture motion.

Motion diagrams.... dots along the path

Graphs... position - time..... velocity - time





Samples and how to think

Motion Diagram... Constant acceleration pattern

Velocity pattern... 0, V, 2V, 3V, 4V, etc.... a = DV/Dt

Position pattern .........Intervals X, 3X, 5X, 7X

Putting same information in a Graph

Velocity Time Graph... slope: a = DV/Dt

Position Time Graph... slope: V = DX/Dt


Analyzing motion with vectors of Velocity, Acceleration


Interactive Physics samples of motion... apath, aperp, v


Discussion of Test



Changing from Kinematics to Dynamics... introduce mass, m, of object that is moving with velocity, V, and has acceleration, a.


Interactive Physics... the Pendulum.


Multiplying V and a vectors by mass m

m V is called "motion" or momentum

m a is called "net force"... F = ma

Newton stated that the net external force on a body causes acceleration of the body

a = DV/Dt

m a = D(mV)/Dt

F = m a = D(mV)/Dt

Interactive Physics with Pendulum... adding Ftotal.

But what are real forces.

Non-contact forces.... Gravity F = G M m/r^2 = m g

Contact force... String

Add Gravity and String forces to Pendulum

So where did Ftotal come from... diagonal of parallelogram.

Other types of forces.

Interactive Physics ... block on surface.