A student drops a pebble from the edge of a vertical cliff. The pebble hits the ground 4 s after it was dropped. What is the velocity of the pebble just before it hits the ground? A. 20 m/s
B. 40 m/s
C. 60 m/s
D. 80 m/s

The summit of chimborazo, in ecuador, which is at a distance of about 6,384 km from the earth's center. the bottom of the mariana trench, in the western pacific ocean, which is nearly 6,370 km from the center of the earth. on the surface of earth on the equator line.

Abearing is designed to a reduce friction b. support a load c.guide moving parts such as wheels, shafts and pivots d. all of the above

When an object is heated it contracts. a. true b. false