We shine light of three different wavelengths—333 nm, 430 nm, and 649 nm—on a metal surface. the observations for each wavelength, labeled a, b, and c, are: observation a: no photoelectrons are observed. observation b: photoelectrons with a kinetic energy of 159 kj/mol are observed observation c: photoelectrons with a kinetic energy of 48 kj/mol are observed

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.

This is the substance(s) formed in a chemical reaction.

Amachinist turns the power on to a grinding wheel, at rest, at time t = 0 s. the wheel accelerates uniformly for 10 s and reaches the operating angular velocity of 96 rad/s. the wheel is run at that angular velocity for 40 s and then power is shut off. the wheel slows down uniformly at 1.5 rad/s2 until the wheel stops. in this situation, the time interval of deceleration is closest to: