Neglecting friction if a pendulum bob has 100 joules of kinetic energy at the bottom of its swing how much potential energy does it have at the top of its swing

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?

Which type of reaction is shown in this energy diagram ?

Which planets are visible without a telescope