Why does ice melt faster in alcohol than in water?

Determine the amount of work done when a crane lifts a 100-n block form 2m above the ground to 6m above the ground

Arunner is training for an upcoming marathon by running around a 100-m-diameter circular track at constant speed. let a coordinate system have its origin at the center of the circle with the x-axis pointing east and the y-axis north. the runner starts at (x, y) = (50 m, 0 m) and runs 2.5 times around the track in a clockwise direction.

Why do astronauts in the space shuttle weigh less?