Validity of an experiment is based upon: a. performing a fair test, in which only the dependent variable affects the independent variable. b. using multiple independent variables. c. using a control group. d. performing a fair test in which only the independent variable affects the dependent variable.

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

Which notation is used to represent an alpha particle? a. b. c. d.

Your science teacher brings in a speaker to talk to your class about climate change. during the session, students ask a few questions. which questions are related to the current evidence on climate change