The jet plane has
a speed of 100 m/s which is decreasing at a rate of 50 m/s^{2}
when it reaches A. Evaluate the magnitude of its acceleration at this
point.

a. 63.3 m/s^{2}
b. 64.6 m/s^{2}
c. 66.5 m/s^{2}
d. 65.7 m/s^{2}

Given data:
y = 25 ln(x/70)
a_{t} = 50 m/s^{2}
v = 100 m/s

dy/dx = 25/x
d^{2}y/dx^{2} = -25/x^{2}

When x = 70 m
dy/dx = 25/70
d^{2}y/dx^{2} = -25/70^{2}

Substituting the above
values in the expression for r, we have
r = 234.67 m