The previous problem considered the body to be falling without friction. If there exists a frictional
fo rce , proportional to the velocity r dY
d t
the equation of motion becom es
d 2 y
„ d Y , m
m - d R + c d T +
9 =
0
d 2 y _
c
d y
d t 2
m
d t
The basic computer circu it is shown in Figure 27.
Figure 27
FALLING BODY PROBLEM CIRCUIT.
FRICTIONAL FORCE ADDED.
This circu it is set up on the computer as before, with the addition of a feedback resisto r a cro ss
the first am plifier. For sim plicity, therelayand ground connections are omitted as w ell as the
initial condition power supply connections. These are the same as in the previous problem .
The solution is shown in Figure 28.
Figure 28 A
Figure 28 B
191
SOLUTION OF FALLING BODY PROBLEM WITH FRICTIONAL FORCE
(a) As displayed on o scilloscop e.
SPRING-MASS SYSTEM
(b) As shown on pen record er.
Page 24
Figure 29
