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 .

the closer the planet is to the sun, the larger the gravity

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min