858 
Junior Examination Papers, 1890. 
EXAMINATION IN MECHANICS AND NATURAL PHILOSOPHY. 
Maximum Number of Marks, 200. Pass Number, 75. 
Wednesday, November 12, 1890. {Three hours allowed.) 
1. Weights of 1, 3, 2, 6 lb. are placed at the angular points A, P>, C, D of 
a square ; find the perpendicular distance of their centre of gravity from A B 
and from A D. 
If the square thus loaded were hung up by the angular point A, show in a 
diagram the position in which it would come to rest. 
2. State briefly what is meant by the " triangle of forces." 
A B is a uniform rod that can turn freely round the end A ; the end B is 
fastened by a thread to a fixed point C, vertically over A, and D is the middle 
point of B C ; specify the forces that keep A B in equilibrium, and show that 
A D C is a triangle for the forces. 
3. Given three separate pulleys, show in diagrams any two ways of com- 
bining them into a " system." 
If the weight to be supported is 1,000 lbs., find the power that will do it 
in each of the two systems. 
4. State Newton's three laws of Motion, and give his illustrations of the 
third law. 
5. If a particle moves in a straight line and in such a way that in each 
second its velocity is increased by 10 feet a second, find the distance it will 
describe from rest in 7 seconds. 
6. Two bodies P and Q are connected by a fine thread, which rests on a 
smooth point ; if the mass of Q is 8 lb., find the mass of P that in falling it 
may draw Q up in such a way that in each second the velocity is increased by 
10 feet a second (^ = 32). 
7. Define specific gravity. What substance is commonly taken as the 
standard in measuring the specific gravity of a solid or liquid ? 
The specific gravity of copper being 8 8, what would be the apparent weight 
in water of a piece of copper which weighs 33 oz. in air 1 
8. Describe briefly the siphon, and how it is used. A and B are two 
vessels containing water, and A is above B ; one leg of a siphon dips into the 
water in A, the other into the water in B ; explain why the water will flow 
from A to B and not from B to A. 
If the above system were first put in action at the sea-level, and afterwards 
at a considerable height (say several thousand feet) above the sea-level, what 
difference would there be in the action of the siphon in the two cases ? 
9. Define the capacity of a body for heat, and the specific heat of a body. 
A pound of lead at 212° F., when put into 1 lb. of water at 5,7°F., is 
found to raise the temperature of the water to 62°F., and no more ; what 
inference might be drawn from this experiment as to the specific heat of water 
and of lead ? 
10. What is meant by the indicated horse-power of a steam-engine ? 
The area of the piston of a steam-engine is 2,000 square inches, and its 
stroke is G feet long; when it is working at the rate of ten strokes a minute 
its indicated horse-power is 100; what is the effective pressure of the steam? 
