A student must design an experiment to determine the gravitational mass of an object. Which of the following experiments could the student use? Select two answers.

A
Place the object on one side of a lever at a known distance away from a fulcrum. Place known masses on the other side of the fulcrum so that they are also placed on the lever at known distances from the fulcrum. Move the known masses to a known distance such that the lever is in static equilibrium.

B
Place the object on a surface of negligible friction, and pull the object horizontally across the surface with a spring scale at a nonconstant speed such that a motion detector can measure how the object's speed as a function of time changes.

C
Place the object on a surface that provides friction between the object and the surface. Use a surface such that the coefficient of friction between the object and the surface is known. Pull the object horizontally across the surface with a spring scale at a nonconstant speed such that a motion detector can measure how the object's speed as a function of time changes.

D
Place the object on the end of a vertically hanging spring with a known spring constant. Allow the spring to stretch to a new equilibrium position, and measure the distance the spring is stretched from its original equilibrium position.