A child pushes down on a box lid with a force of 25 N. At the same time, her friend pushes down on the lid with a force of
30 N. The spring on the box lid pushes upward with a force of 60
N. Can the children close the box? Why or why not?

Which of the following types of electromagnetic radiation has the longest wavelength? a. infrared light b. visible light c. ultraviolet light d. microwaves

The ability to make things happen is also called a. heat b. force c. matter d. energy

When oxygen reacts with hydrogen, it has the capacity to release 29 kilojoules of energy. inside a fuel cell, oxygen reacts with hydrogen to produce 23 kilojoules of useful energy. the rest of the energy is lost as heat. what's the efficiency percentage of the fuel cell?