A student wants to know if the effect of gravity is the same on all objects. She follows these steps:

1. Drop a 5-gram ball, a 10-gram ball, and a 12-gram ball from a height of 10 meters.

2 Record how long it takes for each object to hit the ground

3: ?
Which step should be next?

Choose new balls

Measure the mass of the balls again

Drop the balls from a different height

Perform a second trial