Arock is dropped from a height of 2.5 meters. what is it’s velocity when it reaches the ground? 3.5 meters/second

7.0 m/s

Explanation:

The question is on Free-Fall

In a free fall, an object falls freely without only gravity acting on it. Velocity at the top is zero m/s

Height of fall, h=1/2gt²

Velocity, v=gt where g is gravity acceleration=9.8m/s² and t is time taken fall the fall

Finding the t taken for the fall;

h=2.5m but we know h=1/2gt²⇒substitute values in this equation

2.5=1/2×g×t²

2.5=1/2×9.8×t²⇒2.5=4.9t²

make t subject of the equation;

t²=2.5/4.9

t=√2.5/4.9 =0.7143sec

Finding the velocity

v=gt

v=9.8×0.7143=7m/s

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂