Which best explains why a wood-burning fireplace does not represent a closed system? a. because a fire requires oxygen from the atmosphere to burn b. because the ashes have to be swept away c. because they are not all made of brick d. because they can be used for cooking

Ameter stick is pivoted at the 0.50-m line. a 3.0-kg object is hung from the 0.15-m line. where should a 5.0-kg object be hung to achieve equilibrium (the meter stick oriented horizontal and motionless)?

Boxing gloves are padded to lessen the force of a blow. (a) calculate the force exerted by a boxing glove on an opponent’s face, if the glove and face compress 7.50 cm during a blow in which the 7.00-kg arm and glove are brought to rest from an initial speed of 10.0 m/s. (b) calculate the force exerted by an identical blow in the gory old days when no gloves were used and the knuckles and face would compress only 2.00 cm. (c) discuss the magnitude of the force with glove on. does it seem high enough to cause damage even though it is lower than the force with no glove?

The photo shows sugar dissolved into a solution with excess sugar at the bottom of the jar this type of solution is classified as a. unsaturated b. compound c. saturated d. plasma