Explain the working and principle of perisocope.​

69. air frictionthe velocity of the satellitea. decreases b. increases c. sometimes increases sometimedecreases d. no effect at all70. the unit of gravitational potential energy isa.jouté b.watt c. newtond.pascal71. which of the following is not influenced by a magneta. cobalt b.copper c.irond. nickel72. one joule of work done in one second by unit positive chargea.1 watt b.1 volt c.1 js d. none73. the most deviated colour of light after passing through a prisea. violet b.red c. green d.yellow4. a coin is placed below a beaker fill with water upto 12 cm isdisplaced by water isa. 9cm b.6cmс.3cmd.7cm

Hunter is in lab. he clears a spot on his lab bench to start working. he also puts his lab coat and goggles on. he then identifies where all of the safety equipment is. he notices his station is next to the fume hood, which ventilates the chemicals stored there. the noise of the fume hood was bothersome, so hunter turned it off. which could be an error in his set-up? he should not turn off the fume hood.  he should wait to put on his coat until after the directions are given.  he should wait to put on his goggles until after the directions are given.  he should not sit next to the fume hood. 

List and describe three ways that humans can change ecosystems and three ways that humans can protect ecosystems.