xcii  Agricultural  Education — Examination  Papers,  1883. 
EXAMINATION  IN  MECHANICS  AND  NATURAL 
PHILOSOPHY. 
Maximum  Number  of  Marks,  200.  Pass  Number,  100. 
Thursday , May  10th,  from  10  a.m.  till  1p.m. 
1.  What  are  the  fundamental  units  of  distance,  time,  and  mass 
commonly  used  in  England ; and  how  are  they  respectively  fixed  ? 
2.  State  the  condition  of  the  equilibrium  of  three  forces  acting  at 
a point  called  the  “ triangle  of  forces.” 
Show  by  a diagram  drawn  to  scale  how  three  forces  of  15,  18  and 
21  units  respectively  can  be  made  to  act  at  a point  so  as  to  balance 
one  another.  Describe  an  experiment  by  which  the  accuracy  of  your 
construction  might  be  tested. 
3.  State  the  rule  for  finding  the  centre  of  gravity  of  two  particles 
whose  masses  are  given. 
What  is  a particle  ? 
Particles  whose  masses  are  3 lbs.,  4 lbs.,  7 lbs.,  are  placed  one  at 
each  end  of  three  corners  of  a square,  laid  flat  on  a table ; show  by  a 
construction  drawn  to  scale,  where  a particle  whose  mass  is  14  lbs. 
must  be  placed  that  the  centre  of  gravity  of  the  four  particles  may 
be  at  the  fourth  corner  of  the  square. 
4.  A rod  (A  B)  10  feet  long  can  turn  freely  round  a point  C 
between  A and  B,  and  distant  2 feet  from  B ; a weight  of  20  lbs.  is 
tied  to  the  end  A,  and  one  of  60  lbs.  to  the  end  B ; the  rod  is  kept  in. 
a horizontal  position  by  resting  on  a fixed  point  4 feet  from  C ; what 
is  the  pressure  on  that  fixed  point  and  on  C ? What  would  the  rod 
in  this  question  be  called,  if  considered  to  be  a simple  machine? 
What  would  the  fixed  point  C be  called  ? No  notice  of  the  weight 
of  the  rod  is  taken  in  the  question ; under  what  circumstances  are 
we  justified  in  thus  neglecting  the  weight  of  the  rod? 
5.  What  is  the  number  of  foot-pounds  of  work  done  when  a weight 
of  3§-  tons  are  lifted  vertically  through  25i  feet?  If  this  were  done 
in  a quarter  of  a minute,  what  is  the  horse-power  of  the  agent  doing 
the  work  ? 
6.  What  is  meant  when  the  velocity  of  a body  is  said  to  undergo  a 
constant  or  uniform  acceleration  ? How  is  such  an  acceleration 
measured  ? 
A body  moving  from  a state  of  rest  under  the  action  of  a constant 
force  describes  a distance  of  300  feet  in  the  first  half  minute  of  its 
motion ; what  is  the  accelerative  effect  of  the  force  on  the  body  ? 
What  ratio  docs  the  force  producing  the  motion  bear  to  the  force  of 
the  gravity  on  the  body  (y  = 32)  ? 
7.  Define  the  specific  gravity  (or  specific  density)  of  a solid  or 
liquid,  and  describe  the  usual  method  of  finding  the  specific  gravity 
