Calendar: 1869-1870 Page 518

520 APPLIED SCIENCES make body slide either up or down plane makes an angle φ with the plane Find the least force required to draw the block of wood of the last question up rough plane sin φ 27 which is inclined at an angle of 30 to the horizon and find the pressure on the plane If the force ceases to act and the body runs 500 feet down the plane how far will it run along the horizontal plane at the bottom What is meant by the line of resistance in structure roof square foot of which weighs 1414 lbs is 40 feet in span and has pitch of 45 and is supported by walls of brick- work which are 20 inches thick find the equation to the line of resistance If the wall be 21 feet high and be supported by buttresses foot deep how high must they reach to keep the wall from falling river wall of brick-work 20 feet deep feet thick at the top sustains the pressure of water on its sloping face to within feet of the top find the thickness at the bottom that the line of resistance may cut the base inches within the extrados Define virtual velocity and virtual moment State the principle of virtual velocities Employ it to deter- mine the position of equilibrium of rod 16 feet long which rests on post at distance of feet from smooth wall and with one end resting against the wall What is meant by energy Distinguish between potential and actual energy Find the loss of energy when an imperfectly elastic ball of given weight strikes fixed plane at given angle of incidence perfectly elastic ball is projected with velocity of 16 feet per second at an angle of 60Q to the horizon and strikes plane inclined at 30 to the horizon which passes through tbe point of projection find where it strikes the plane at the first second third and fourth rebound and the velocities at those points How are the faces of teeth formed on the driver when there are pins on the follower and how is the size of the pins taken into account What modification takes place when rack is substituted for one or other of the toothed wheels