2. Ramer wants to find out how pressure affects the force of gravity acting on dust particles in a cloud. Tamer designs an experiment in which he places dust particles in a pressure chamber.
He is able to adjust the pressure in the chamber from 0 Pascals to 780 Pascals. What should
Tamer use as his control group?
1. a sample of dust particles at 0 Pascals
2. He does not need a control group.
3. a sample of dust particles at 780 Pascals
4. a sample of dust particles in Earth's atmosphere