Students connect a spring scale to a block on a rough horizontal surface. the students use the spring scale to measure the magnitude of the horizontal force needed to pull the block at a constant speed. which of the following statements explains why two forces exerted between objects ar equal in magnitude? a the gravitational and normal forces exerted on the block, because they are a newton's third-law pair. the frictional force and force exerted by the spring scale on the block, because they are a newton's third-law pair. the normal force and the frictional force exerted on the block, because objects always exert forces of equal magnitude on each other. the frictional forces that the block and the surface exert on each other, because objects always exert forces of equal magnitude on each other.

The frictional force and force exerted by the spring scale on the block, because they are a Newton's third-law pair.

Explanation:

Newton's law states that every action has an equal and opposite reaction. These forces act on different bodies but are equal.

Hence, the frictional force and force exerted by the spring scale on the block are equal in magnitude because they are a Newton's third-law pair.

  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

ok

explanation: