621. Which of the following is not the unit of work, energy and heat ?
A.Kcal
B.Kg m
C.KWhr
D.Hp

622. The weight of a body is due to
A.Centripetal force of earth
B.Gravitational force of attraction towards the centre of the earth
C.Forces experienced by body in atmosphere
D.Force of attraction experienced by particles

623. The forces, which meet at one point, but their lines of action do not lie in a plane, are called
A.Coplanar non-concurrent forces
B.Non-coplanar concurrent forces
C.Non-coplanar non-concurrent forces
D.Intersecting forces

624. When trying to turn a key into a lock, following is applied
A.Coplanar force
B.Couple
C.Lever
D.Moment

625. According to principle of transmissibility of forces, the effect of a force upon a body is
A.Maximum when it acts at the centre of gravity of a body
B.Different at different points in its line of action
C.The same at every point in its line of action
D.Minimum when it acts at the C.G. of the body

626. Which of the following is a vector quantity
A.Energy
B.Mass
C.Momentum
D.Angle

627. The magnitude of two forces, which when acting at right angle produce resultant force of ?10kg and when acting at 60° produce resultant of ?13kg These forces are
A.2 and ?6
B.3 and 1 kg
C.?5 and ?5
D.2 and 5

628. A number of forces acting at a point will be in equilibrium if
A.Their total sum is zero
B.Two resolved parts in two directions at right angles are equal
C.Sum of resolved parts in any two perpendicular directions are both zero
D.All of them are inclined equally

629. Two non-collinear parallel equal forces acting in opposite direction
A.Balance each other
B.Constitute a moment
C.Constitute a couple
D.Constitute a moment of couple

630. According to principle of moments
A.If a system of coplanar forces is in equilibrium, then their algebraic sum is zero
B.If a system of coplanar forces is in equilibrium, then the algebraic sum of their moments about any point in their plane is zero
C.The algebraic sum of the moments of any two forces about any point is equal to moment of their-resultant about the same point
D.Positive and negative couples can be balanced

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