Isaac invents a machine that him mow the lawn. the work output of the machine is 10 foot-pounds. the work input is 20 foot-pounds. what is the efficiency of isaac's machine? i realy need with this plz me with thisi dont want to fail physics a.)1 b.)2 c.)5 d.)0.5

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)