Explain what happens when a massive star ends its life as a supernova

If a stone with an original velocity of 0 is falling from a ledgeand takes 8 seconds to hoybthe ground whays the final velocity of the stone

Arunner is jogging at a steady 3.6 km/hr. when the runner is 2.9 km from the finish line, a bird begins flying from the runner to the finish line at 14.4 km/hr (4 times as fast as the runner). when the bird reaches the finish line, it turns around and flies back to the runner. even though the bird is a dodo, we will assume that it occupies only one point in space, i.e., a zero-length bird. how far does the bird travel? (b) after this first encounter, the bird then turns around and flies from the runner back to the finish line, turns around again and flies back to the runner. the bird repeats the back and forth trips until the runner reaches the finish line. how far does the bird travel from the beginning? (i.e. include the distance traveled to the first encounter)

Aball of mass 0.3kg is released from rest at a height of 8m.how fast is it going when it hits the ground? accleration due to gravity is g=9.8m/s