Question

calculations with potential and kinetic energy

Answer 1

Max Potential energy at point of release = 0.75 x 9.81 x 0.6 = 4.4145 J

This will also equal the maximum kinetic energy due to conservation of energy.

If I remember right the velocity scales with the cos of the angle between the sting and a perpendicular line from the top of the pendulum to the floor. So if it is 45 cm from the top of its swing then the angle is 22.5.
Cos 22.5 = 0.923879

Kinetic energy scales with the sqaure of of the speed,

so if the speed is 0.923879 of its max
the kinetic energy is 0.923879 squared of its max = 0.85455 of its max

So Kinetic energy at this point is 0.85455 x 4.4145 = 3.768 Joules

Potential Energy = 4.4145 - 3.768 = 0.646488 Joules

Answer 2

im still confused