Radio waves heading upward from earth often bounce off the
a. troposphere b. mesosphere
c. stratosphere
d. thermosphere

Aspring with a mass of 2 kg has a damping constant 14 kg/s. a force of 3.6 n is required to keep the spring stretched 0.3 m beyond its natural length. the spring is stretched 0.6 m beyond its natural length and then released. find the position of the mass at any time t. (assume that movement to the right is the positive x-direction and the spring is attached to a wall at the left end.)

Density of salty water as compared to the density of pure water is(a) is less(b) is always equal(c) is always more(d) may be less or more

Spend time observing or thinking about events that involve matter and energy. which events can you explain? which events can’t you explain?