
215Dynamics Review
We now will examine the acceleration whose direction is once more specied by the right-
hand rule. We shall dene the position of point, P, by the position vector, r, as shown in
Figure 7.14. We can then write the acceleration, a, in terms of radial and circumferential
components as discussed earlier.
We need to recall Equation 7.42 and note that dr/dt = 0. This leaves us with
e=−
+
r
t
r
t
r
d
d
d
d
θ
2
2
2
(7. 54)
Here we need to note that the rst term is negative because it acts in the negative radial
direction. Now, from our previous denitions we can rewrite Equation 7.54 as
=− +
ω
2
α
θ
(7. 55)
We can dene ...