What must be the distance between source of sound and mountain to give an echo in 5 seconds ? ,(speed of sound at 0°c=33m\sec

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.

Scientific models are based on current knowledge, which can limit their effectiveness when new discoveries are made.

Which are causes of mechanical weathering? (check all that apply) a. acid rain b. plant growth c. animal actions d. carbon dioxide e. pressure release i chose b & e and got the question wrong.