A simple machine has efficiency 90%. What does it mean? No machine has 109 efficiency, why?​

Efficiency of a machine is 90% this means that the total energy produced to the machine only 90% is useful and given as a output.

Machines are not 100% efficient because some of the work done by a machine is used to overcome friction

Explanation:

A simple machine has efficiency 90% means that 10% of the applied effort is wasted due to overcoming friction and 90% of the applied force is used in doing useful work .No machinr has hundred percent efficiency because every machine is affected by overcoming friction .

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2