A sky diver jumps from a helicopter and is falling straight down at 30 m/s when his parachute opens. From then on, his downward acceleration is approximately
a = g - cv2 , where g = 9.81 m/s2 and c is a constant. After an initial "transient" period, he descends at a nearly constant velocity of 5 m/s.

a. What is the value of c, and what are its SI units?

b. What maximum deceleration is the sky diver subjected to?

c. What is his downward velocity whe he has fallen 2m from the point at which his parachute opens?

A1200 kg car traveling north at 10 m/s is rear-ended by a 2000 kg truck traveling at 30 m/s. what is the total momentum before and after the collision?

While studying chemical reactions and conservation of matter, sarah's class conducted a variety of experiments. sarah and her lab partner found the mass of a wax candle and placed the candle in a flask. the students lit the candle and let it burn to completion. all that was left was wax and charred candle wick. per their teacher's instructions, the students found the mass of the products. their data can be seen in the data table. formulate a hypothesis the students could test to explain why the experiment did not support the law of conservation of matter. a) the students could repeat the experiment using different candles; there might have been a flaw in the candle. b) the experiment should be repeatable. the students should run several trials and then take an average of the after mass in each trial. c) the students should have someone in the class check their measurement skills as they repeat the experiment. they may have made an error using the balance. d) the students should burn the candle in a container that has some type of lid so that any gas that is a product of the reaction can be contained and massed. submit

In a hydrogen molecule there are a total of four charges, 2 protons in the two nuclei, and 2 electrons. how many unique charge-pairs are there (without double counting)?