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the city is using sand trucks to place sand on the road during icy conditions. which best explains the use of sand?

a. the sand increases friction by increasing surface area.
b. the sand increases friction by increasing roughness.
c. the sand decreases friction by increasing surface area.
d. the sand decreases friction by increasing roughness.

0.2348 grams of pbcl2 used to form 44.0 ml of solution.

The twister and runaway train are two coasters at the same amusement park. both coasters start at the same height. the coaster for the twister is twice the mass of the coaster for the runaway train. which roller coaster has greater gravitational potential energy at the start of the ride?

The content of manganese (mn) in steel was determined spectrophotometrically and with the use of the standard addition method. an unknown sample of mn from a digested steel sample gave an absorbance of 0.185 when analyzed spectrophotometrically. when 5.00 ml of solution containing 95.5 ppm mn was added to 50.0 ml of the unknown steel solution (digested sample), the absorbance was 0.248. calculate the concentration, in parts-per-million (ppm), of mn in the digested steel sample solution.