Which of the following lab set-ups could be used to determine the gravitational mass of an object in a classroom?
A spring with a known spring constant is hung vertically. The object is attached to the spring and the elongation of the spring is measured.
A string that attaches the object to a 20 kg mass is placed over a pulley. When released, the 20 kg mass falls pulling the object across a frictionless surface. The time it takes the object to move 0.5 m is measured.
The object is placed on a frictionless table. A pendulum that was initially held horizontally is released and hits the object at its lowest position. The mass and length of the pendulum are known. The time it takes for the object to move 0.5 m is measured.
The object is held 2.5 m above the ground and released from rest. The time it takes for the object to land is measured. Air resistance can be ignored in this situation.