Problem Sheet – Thrust on Immersed Surfaces
Shane Murray
Dept. of The Built Environment,
Institute of Technology, Carlow
1.
A tank 1.2m high, 0.9m wide & 2.4m long if filled with water. Find the total force & the position
at which it acts for (a) an end, (b) a side, (c) the base. http://screenr.com/2uc &
http://screenr.com/1uc
2.
A lock gate is a rectangular section 7.2m wide. The depth of water on the lower side is2.4m, the
depth on the opposite side is h meters. The maximum allowable resultant thrust is 1.5MN.
Calculate the maximum value of h if this thrust is not to be exceeded. http://screenr.com/Cuc
3.
A sluice gate 0.9m wide, 1.8m deep, weighs 3.5kN & works in vertical guides. The water surface
on one side of the gate is 0.3m below the upper edge of the gate. If the coefficient of friction
between the gate & the guides is 0.4, find the force required just to lift the gate.
http://screenr.com/Ouc
4.
A dock gate 18m wide has sea-water of density 1.03Mg/m3 to a depth of 6m on one side & 3m
on the other. Find (a) the resultant thrust on the gate, (b) the resultant moment tending to overturn
the gate about its lower edge.
http://screenr.com/fuc & http://screenr.com/HEc
5.
A dock gate 6m high & 9m wide is pivoted at its base A & held vertical by a cable (which is at
30o to the horizontal) at the top of the gate. There is a total depth of 3m of salt water of density
1.03Mg/m3 on one side of the gate. Find the tension in the cable.
http://screenr.com/xEc &
http://screenr.com/CEc
6.
A tank of water has vertical sides & a rectangular opening in one end. The opening is covered by
a door hinged along its top edge A & held by four bolts at the lower end B. The opening is 0.6m
wide & 1.5m deep & the hinge at A is 1.2m below the water surface. Find (a) the depth at which
the resultant water thrust acts on the door, (b) the load on each bolt, (c) the load on the hinge at
A. http://screenr.com/OEc & http://screenr.com/CYc
7.
A tank with vertical sides contains oil of relative density 0.8 to a total depth of 1.8m. A hole
0.6m diameter is covered by a trap door, the lowest point of which is level with the base of the
tank. Find (a) the total thrust on the door, (b) the depth below the surface of the line of action of
this thrust. http://screenr.com/XYc
8.
A vertical dock gate of rectangular section 2.4m deep & 1.2m wide pivots about a hinge at its
lower edge. It is held in position by 4no. 12mm diameter cables attached to its upper edge. The
cables are at 45o to the horizontal. If sea-water has a density of 1.03Mg/m3, calculate (a) the
maximum thrust on the dock gate, (b) the stress in the cables, (c) the vertical & horizontal forces
on the hinge.
http://screenr.com/GYc & http://screenr.com/kYc & http://screenr.com/uYc
9.
A dam face is inclined at 500 to the water surface. The dam is 18m wide and the depth of water is
6m. Calculate (a) the total force on the dam face, (b) the depth below the water surface at which
the resultant force acts.
http://screenr.com/Hbc & http://screenr.com/xbc
10. The side of a tank makes 450 with the water surface. A trap door 0.3m in diameter is hinged at a
point 0.9m below the water surface and bolted against the water pressure at the lowest point of
the door. Calculate (a) the force in the bolt, (b) the load on the hinge. http://screenr.com/Wbc &
http://screenr.com/mbc
11. A tank of oil of relative density 0.8 contains a rectangular trap door 3.0m wide and 2.4m deep.
The door makes an angle of 1100 with the line of the oil surface and is hinged at a point 0.6m
vertically below the surface. If the door is held against the oil pressure by four bolts along its
lower edge, find the force in each bolt.
http://screenr.com/Fbc & http://screenr.com/tbc