Avariable star is one whose brightness alternately increases and decreases. for the most visible variable star, delta cephei, the time between periods of maximum brightness is 5.4 days, the average brightness (or magnitude) of the star is 4.0, and its brightness varies by 60.35 magnitude. find a function that models the brightness of delta cephei as a function of time.

Consider an ordinary, helium-filled party balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.

What type of relationship exists between the length of a wire and the resistance, if all other factors remain the same? o a. resistance is directly related to length. ob. resistance is directly related to the square of the length. c. resistance is inversely related to the length. d. resistance is inversely related to the square of the length. reset next

Apulley with mass mp and a radius rp is attached to the ceiling, in a gravity field of 9.81 m/s2 and rotates with no friction about its pivot.