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.the balanced   chemical equation is as below

cu +   2 ag(no)₃ → cu(no₃)₂   +2 ag

2.the   much silver   produced   is   50.9 g

step 1: find the   moles of cu

moles =   mass÷   molar mass

  from periodic table the molar mass of cu = 63.5 g/mol

moles is therefore = 15.00 g÷ 63.5 g/mol = 0.236   moles

step 2: use the mole ratio to determine the   moles of ag

from equation above   cu: ag   is 1: 2

therefore the moles of ag   =0.236   moles   x 2/1 =0.472   moles

step 3: find the mass   of ag

mass = moles x molar mass

from periodic table   the molar mass of ag =107.87 g/mol

mass   = 0.472   moles x 107.87 g/mol = 50.9 g

3.   the   much   silver   collected worth is   1.797 oz

  convert   50.9 g   to oz

that is   1 gram = 0.0353 oz

          50.9 grams =?   oz

by cross multiplication

={(50.9 grams x 0.0353 oz) / 1   gram}   =1.797 oz