mariah wrote:A mechanic system consists of a large gear and a little gear. The rating life
of the gear is 6000,000 rounds. What is the life of the whole system?
1). The ratio between two radius is Â…2/5
2). It cost 2 minutes for the little gear to round one circle.
dont have oa
IMO B
At first glance this question seems like out of syllabus but now i think this question actually based on common sense...please try to understand my approach and correct me if m wrong..
The key is to understand that:--
the life of the system depends on small gear..the moment small gear stop the whole system fails...see explanation why...
see as given we have 2 type of gears, one is large and one is small...now try to visualize or sketch the gears in shape of 2 circles or wheels thats better...its but obvious that they are connected...
Now...second thing that is obvious is that the Large gear has bigger radius than the smaller one..
Now if u want to calculate the area covered by a wheel then its actually the perimeter..
I.e 2*pie*R
that means that the large gear travel more in one round then the smaller gear..because of the large radius..see the formula...
But since as i told earlier, both the gears are connected and plus...they have a set life...That means suppose the mechanical system travels a total distance let say, X, then
the large gear takes less rotation then smaller one...this point is the key..
means the no of rounds of the total mechanical system of the life depends on the small gear..
because the mechanical system travel only that much distance that small one can travel...the moment small gear stop the whole system stop..so small gear is deciding the life of the whole system
Now the question asks about life that means we need years or some time related quantity but its not there in Op A hence A alone is insufficient.
In B, the time taken by the small gear is given = 2 mins
and as i explained above the life of the system depends on small gear..the moment small gear stop the whole system fails
hence we get, 2min * 6000,000 rounds = 12,000,000 mins as the life of whole system..
Op B is sufficient
