Amechanical device requires 500j of work to do 200j of work in lifting a box. what is the efficiency of the device?

Why do electron microscopes have higher resolving power than light microscopes?

Samir watches a 100-minute movie on his spaceship. maria's spaceshipe flies in the same direction as samir's spaceship but she observes his move to last 125 minutes and his spaceship to be 40 m long. how long does samir observe his own spaceship to be? according to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does marias voyage take according to samir?

Explain what will happen if decomposers were apsent from a forest ecoysystem.