Is it true? people should develop the habit of negative self-talk to boost their confidence?

Astone dropped into a well is heard to strike the water after 8seconds. find the depth of the well if the velocity of sound is 350m/s

Ateam of astronauts is on a mission to land on and explore a large asteroid. in addition to collecting samples and performing experiments, one of their tasks is to demonstrate the concept of the escape speed by throwing rocks straight up at various initial speeds. with what minimum initial speed vesc will the rocks need to be thrown in order for them never to "fall" back to the asteroid? assume that the asteroid is approximately spherical, with an average density p 3.84 x108 g/m3 and volume v 2.17 x 1012 m3 recall that the universal gravitational constant is g 6.67 x 10-11 n m2/kg2

Suppose a comet has an orbital period of 309.1 years around the sun. what is it’s average distance from the sun?