If the work output of a simple machine is 40 j and the work input is 50 j, the percent efficiency is %.
a. 5/4
b. 10
c. 80
d. 90

Efficiency = (Work out / Work In) * 100

Efficiency = (40 / 50) * 100

Efficiency = 0.8 * 100

Efficiency = 80%

The efficiency of any machine has to be less than 100%. If it is not, patent whatever you are doing. It will make you instantly wealthy.

  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