Horium-229 is the radioactive substance that gives lantern mantels their eerie glow. The half life of thorium-229 is 7340 years.

If one mantel consists of 0.25 grams of thorium, how much thorium will remain after 14,680 years?

Aferris wheel is a vertical, circular amusement ride with radius 9 m. riders sit on seats that swivel to remain horizontal. the ferris wheel rotates at a constant rate, going around once in 9 s. consider a rider whose mass is 56 kg. at the bottom of the ride, what is the perpendicular component of the rate of change of the rider's momentum? at the bottom of the ride, what is the vector force exerted by the seat on the rider?

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c

The magnitude of the poynting vector of a planar electromagnetic wave has an average value of 0.939 w/m^2 . the wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. how much total electromagnetic energy falls on the area during 1.0 minute?