Agriculhiral Uducation — Examination Papers, 1888. cxxxv 
EXAMINATION IN MECHANICS AND NATURAL 
PHILOSOPHY. 
Maximum Number op Marks, 200. Pass Number, 100. 
Friday, May \ \th,from 10 a.7n. till 1 j^.vi, 
1. Define the centre of gravity of a body. Mention any one case 
in Y/hich the centre of gravity is not a point of the body itself. 
Why is it difficult (or impossible) to balance a rod horizontally 
on your finger ? Why is the difficulty diminished (or removed) when 
a weight is hung from each end of the rod 1 
2. A thread, which hangs over a fixed pulley, carries a body at 
each end ; why will the bodies remain at rest if their weights are 
equal ? What frictions are there in this case tending to keep the 
bodies at rest even when the weights are unequal 1 
•3. Show in a diagram how to combine a fixed and a movable 
pulley info a system for raising a weight. If it is found liy trial 
that when either pulley is fixed (as in Q. 2) a weight of 500 lbs. is 
required to lift off" the ground a weight of 460 lbs., what force 
would be required to lift a weight of 1 ,000 lbs. off the ground, when 
the system shown in your answer to the first part of the question is 
used ? 
4. When a heavy body, such as the trunk of a tree, is moved 
forward on rollers, how much faster than the rollers does the body 
tend to advance, and why ? 
5. Define a foot-pound and a horse-power. 
It is found that by a consumption of 1,200 lbs. of coals a train 
of 60 tons can be made to move over 40 miles against a resistance 
of 7 lbs. a ton ; how many foot-pounds of work are got out of each 
bushel (84 lbs.) of coals consumed 1 
6. A body weighing 10 tons is moving at the rate of 30 miles 
an hour : how many foot-pounds of work is it able to do against a 
resistance ? If the resistance were a constant friction of 8 lbs. a 
ton, how far would the body move before being brought to rest ? 
7. Describe tlie method of finding the specific gravity of a liquid 
by a specific gravity bottle. 
If the bottle when full of water is counterpoised by 988 grains 
and the counterpoise of the empty bottle, and when full of sulphuric 
acid by 1,742 grains and the counterpoise, what is the specific gravity 
of the sulphuric acid ? 
State briefly how the result would be affected by the buoyancy 
of the atmosphere. 
Ti 2 
