You drop a 2 kg book to a friend who stand on the ground at distance d=10.0 m below, if your friends out streched hand at distance d=1.50 m above the ground. (a) how does the work wg does the gravitational force do on the book as it is drop to her hands? (b) what is the change u in the gravitational potential energy of book earth system drop? if the gravitational potential energy u of that system is taken be zero by ground level

Part(a) The work done by gravitational force on the book as it is dropped to her hands is 167 Joules

Part(b) The change in the gravitational potential energy() of book earth system is -167 Joule

Explanation:

Part (a)

Since the work done (W)= Force(F)x Displacement(D) in the direction of force

Here force is applied by gravity in downward direction (towards the center of the earth),

And displacement in the direction of force is D= (10-1.5) m = 8.5 m

Therefore work done ,

where mass, m =2 kg and acceleration due to earth's gravity ,

=>

Thus the work done by gravitational force on the book as it is dropped to her hands is 167 Joules

Part (b)

By the work energy theorem , Change in the gravitational potential energy ()= - Work done by gravitational force ()

=>

Thus  the change in the gravitational potential energy() of book earth system is -167 Joule

  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