Question

where is the speed of simple pendulum maximum ? ​

Answer 1

Use D0EL (energy conservation).

Step 1: Define/draw system and coordinates. (see transparency)

Initial position i and final position f (at the bottom).

Step 2: Define potential energy zero.

Define the zero of the potential energy to be the bottom of the path.

Step 3: Energy conservation statement.

Ui + Ki = Uf + Kf

Initial kinetic energy Ki = 0 because the ball is released from rest.

Final potential energy Uf = 0 by definition.

Conclusion: Ui = Kf or mgh = ½ mvf2,

where h is the height from which the ball is released.

Cancel the m's to give: vf = (2gh)½

Determine h from geometry: h = L - Lcos θ = L (1-cos θ)

With L = 1.40 m and θ = 20o, h = 0.0844 m, vf = (2gh)½ = 1.29 m/s

Answer 2

at mean position of the pendulum