The centre of gravity of a trapezoidal dam section whose top width is a, bottom width is band the vertical side is a, from its vertical face is
(a² + ab + b²)/3 (a + b)
(b² + bc + c²)/3 (b + c)
(a² + ab + c²)/3 (a + c)
None of these
Correct Answer :
A. (a² + ab + b²)/3 (a + b)
Related Questions
A car goes round a curve of radius 100 m at 25 m/sec. The angle to the horizontal at which the road must be banked to prevent sideways friction on the car wheels is tan1 x, where x is (Assume g = 10 m/sec²)
3/8
1/2
9/5
5/8
A Seconds pendulum executes
0.5 beat per second
1.0 beat per second
2.0 beats per second
2.5 beats per second
The reaction at the support B of the beam shown in below figure is 
1.6 t
9.6 t
8.5 t
0.5 t
If the given forces P₁, P₂, P₃ and P₄ are such that the force polygon does not close, then the system will
Be in equilibrium
Always reduce to a resultant force
Always reduce to a couple
Both (A) and (C)
The unit of moments in M.K.S system, is
kg.m
kg/m2
kg/sec2
kg/sec
The C.G. of a right circular cone lies on its axis of symmetry at a height of
h/2
h/3
h/4
h/5
For a simple pendulum, time period for a beat, is
π √(l/g)
π √(2l/g)
π √(g/2l)
π √(l/2g)
One end of a light string 4 m in length is fixed to a point on a smooth wall and the other end fastened to a point on the surface of a smooth sphere of diameter 2.25 m and of weight 100 kg. The reaction between the sphere and the wall of the arrangement made is
102.5 kg
105.5 kg
108.5 kg
110 kg
A light rope is loaded with many equal weights at equal horizontal intervals. The points of suspension on the rope lie on a
Parabola
Catenary
Cycloid
Ellipse
A uniform pyramid and a uniform prism of same height lie with their base on the surface. Which is more stable?
Pyramid
Prism
Both equally stable
None of the above
On a ladder resisting on a smooth ground and leaning against a rough vertical wall, the force of friction acts
Towards the wall at its upper end
Away from the wall at its upper end
Upwards at its upper end
Downwards at its upper end
A spring scale in a stationary lift shows a reading of 60 kg for a man standing on it. If the lift starts descending at an acceleration of g/5, the scale reading would be
48 kg
60 kg
72 kg
None of these
The motion of a bicycle wheel is
Translatory
Rotary
Rotary and translatory
Curvilinear
Time of flight of a projectile on a horizontal plane, is
2u sinα/g
2u cosα/g
2u tanα/g
2u cotα/g
A satellite goes on moving along its orbit round the earth due to
Gravitational force
Centrifugal force
Centripetal force
None of these
The product of mass and velocity of a moving a body, is called
Moment
Momentum
Power
Impulse
The gravitational force makes a satellite go round the earth in a circular orbit, if it is projected with an initial velocity of
8.04 km/sec at a height of 285 km
11.11 km/sec at a height of 37,400 km
11.26 km/sec, the satellite escapes the pull of the earth
All the above
The velocity of a moving body, is
A vector quantity
A scalar quantity
A scalar as well as a vector quantity
None of these
A system of coplanar forces is in equilibrium when
Force polygon closes
Funicular polygon closes
Both force polygon and funicular polygon close
All the forces are concurrent
Williot-Mohr diagram is used to determine deflection in
Trusses only
Beam only
Rigid frames only
Any type of structure
Varingons theorem of moments states
Arithmetical sum of the moments of two forces about any point, is equal to the moments of their resultant about that point
Algebraic sum of the moments of two forces about any point, is equal to the moment of their resultant about that point
Arithmetical sum of the moments of the forces about any point in their plane, is equal to the moment of their resultant about that point
Algebraic sum of the moments of the forces about any point in their plane, is equal to the moment of their resultant about that point
If two forces P and Q (P > Q) act on the same straight line but in opposite direction, their resultant, is
P + Q
P/Q
Q/P
P - Q
Two balls of masses 3 kg and 6 kg are moving with velocities of 4 m/sec and 1 m/sec respectively, towards each other along the line of their centers. After impact the 3 kg ball comes to rest. This can happen only if the coefficient of restitution between the balls is
2/3
1/5
3/5
1/3
The centre of gravity of a triangle is at the point where three
Medians of the triangle meet
Perpendicular bisectors of the sides of the triangle meet
Bisectors of the angle of the triangle meet
None of these
Impulse can be obtained from a
Force-displacement diagram
Force-time diagram
Velocity-time diagram
Velocity-displacement diagram
The velocity ratio of the differential wheel and axle is
R/r1 - r2
2R/r1
3R/r1 - r2
2R/r1 + r2
For a body moving with simple harmonic motion, the number of cycles per second, is known as its
Oscillation
Amplitude
Periodic time
Frequency
A rigid body suspended vertically at a point and oscillating with a small amplitude under the action of the force of gravity, is called
Simple pendulum
Compound pendulum
Second's pendulum
None of these
On a ladder resting on a rough ground and leaning against a smooth vertical wall, the force of friction acts
Downwards at its upper end
Upwards at its upper end
Perpendicular to the wall at its upper end
Zero at its upper end
The force polygon representing a set of forces in equilibrium is a
Triangle
Open polygon
Closed polygon
Parallelogram