Mass is a constant, but weight can change with location. explain. i don't understand

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?

1) what is the power in horsepower of a 100 watt light bulb? what is the power in kilowatts of a 200 horsepower engine? 2) if a cars engine is providing 3000 n of force to keep the car moving at 5 m/s, what is the engine’s effective power? 3) how many gallons of water will be pumped from a well 30 feet deep by a 1/2 hp engine in 1 minute? (1 gallon weighs 8.34 pounds)

Notice how they put future which of the clouds shown would indicate a possible future rain storm? a) b) c) d)