Aman is pulling a 13-kg sled across a flat, snowy surface. he holds the handle of the sled at a 30° angle with the ground.
what is the minimum pulling force (f) to the nearest newton that the man must exert to keep the sled moving? (use the following constants: coefficient of sliding friction = 0.15; acceleration due to gravity = 9.8 m/s2, cos 30 = 0.87.)

a. 9.5 nb. 20 nc. 19 nd. 22 ne. 130 n

The most important difference between a wedge and an inclined plane is a. their size b. their shape c. how they are used d. what they are made of

What is a neurotransmitter involved in mood reward, addiction, and motor behaviors?

Because air contracts as it cools, the air pressure inside a freezer is typically lower than on the outside. why do ice cubes inside a freezer tend to shrink over time? a. the ice dissolves oxygen from the air, forming a denser crystalline matrix. b. the ice reacts chemically with carbon dioxide in the air, forming gaseous carbon compounds. c. the ice melts, and then the liquid freezes as ice crystals on the bottom of the freezer. d. the ice sublimes, and then the water vapor deposits as ice crystals on the sides of the freezer.