A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is above the ground. What is the mass of the box

State one advantage and one disadvantage of using a plane mirrior as a driving mirrior

Photoelectrons with a maximum speed of 6.50 x 107 m/s are ejected from a surface in the presence of light with a frequency of 6.75 x 1014hz. if the mass of an electron is 9.10 x 10-31 kg, calculate in joules the maximum kinetic energy of a single electron. 3.84 x 10-15 j 1.92 x 10-15 j 5.92 x 10-23 j 3.07 x 10-16 j

It is really hard for me right know