Aplanetary nebula is the phase of a

a) star in its late life
b) protostar before it becomes a white dwarf
c) star before it becomes a black hole
d) planet before it becomes a star

Ahollow metal sphere has 6 cm and 11 cm inner and outer radii, respectively. the surface charge density on the inside surface is −100nc/m2. the surface charge density on the exterior surface is:

Spend time observing or thinking about events that involve matter and energy. which events can you explain? which events can’t you explain?

Apulley system is used to lift a 2,000 newton engine up a distance of 3 meters. the operator must apply a force of 250 newtons to the chain of the pulley system to lift the motor. to lift the engine 3 meters, the operator must pull a total of 30 meters of chain through the pulley system. what is the value of di?