How high would you have to raise an object on a pendulum, in relation to the lowest point in its swinging motion, in order to achieve a velocity of 9.9 m/s at the lowest point?

High as 4.9meter

Explanation: Velocity is maximum at the mean position of a pendulum.

At this point Potential energy equals Kinetic Energy.

P.E = K.E

m*g*h = (m*v²)/2

m cancels m

We are left with

g*h = v²/2

g = 10m/s²

h is the height we are calculating for.

V is the velocity 9.9 m/s

h = v²/(2*g)

h = (9.9)²/(2*10)

hieght (h) = 98.01/20

hieght = 4.90 metre

asthenosphere and convection

not too sure thinking all accelerations are pointed down