Krishne wants to measure the mass and volume of a key. which tools should she use?

a balance and a beaker of water
a balance and a meter stick
a beaker of water and a ruler
a ruler and a meter stick

Two masses are connected by a rope that hangs over a pulley as shown below. the pulley is a uniform cylinder of radius 푅=0.381meters and mass 푀=3.1푘푔. initially 푚"is on the ground and 푚#rests 2.5 meters above the ground. if the system is released, use conservation of energy to determine the speed of 푚#just before it strikes the ground. assume the pulley bearing is frictionless.