21. 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
(e) none of the above.
Ans: b
22. When trying to turn a key into a lock, following is applied
(a) coplanar force
(b) non-coplanar forces
(c) lever
(d) moment
(e) couple.
Ans: e
23. Which of the following is not a scalar quantity
(a) time
(b) mass
(c) volume
(d) density
(e) acceleration.
Ans: e
24. According to principle of transmissibility of forces, the effect of a force upon a body is
(a) maximum when it acts at the center 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
(e) none of the above.
Ans: c
25. Which of the following is a vector quantity
(a) energy
(b) mass
(c) momentum
(d) angle
(e) speed.
Ans: c
26. The magnitude of two forces, which when acting at right angle produce resultant force of VlOkg and when acting at 60° produce resultant of Vl3 kg. These forces are
(a) 2 and V6
(b) 3 and 1 kg
(c) V5andV5
(d) 2 and 5
(e) none of the above.
Ans: c
27. 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 per-pendicular directions are both zero
(d) all of them are inclined equally
(e) none of the above.
Ans: c
28. 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
(e) constitute a resultant couple.
Ans: c
29. 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 theiwesultant about the same point
(d) positive and negative couples can be balanced
(e) none of the above.
Ans: b
30. Which of the following is not a vector quantity
(a) weight
(b) velocity
(c) acceleration
(d) force
(e) moment.
Ans: a