a pebble is dropping from a building that is 125m high. THe pebble is initially at rest. approximately how long does it take for the pebble to reach the ground.

Here's the formula you want to use to solve this:

Distance = (1/2) · (acceleration) · (time²)

We know the distance to the ground and the acceleration of gravity, so let's pluggum in:

. . . . . 125 m = (1/2) (9.8 m/s²) (time²)

Divide each side by (4.9 m/s²):  

. . . . . (125 m) / (4.9 m/s²) = time²

. . . . . 25.51 s² = time²

Square-root each side:

5.05 seconds  = time

1.195000

explanation:

total mass=0.0117+0.0137+0.0881+0.0111

total mass= 0.01172kg

total velocity = 0.283-0.743+0.871-0.799+0.155+0.637+0.301=0.102

momentum=mv=0.1172*0.102=1.195000//