What is unusual about the results of mass determinations of clusters of galaxies?

The long handle on a rake is a(n) a. lever b. screw c. wedge d. inclined plane

Aplayer uses a hockey stick to push a puck at a constant velocity across the ice. the weight of the puck is 170 n. the coefficient of friction is 0.0600. with what force must the player push the puck so that his force just equals the frictional force? 28.3 n 0.999 n 0.102 n 0.0104 n

The center of the milky way most likely contains a. empty space. b. a red giant star. c. a globular cluster. d. a supermassive black hole.