41. If the efficiency of a lifting machine is kept constant, its velocity ratio is __________ proportional to its mechanical advantage.
42. Non-coplanar non-concurrent forces are those forces which
A. meet at one point, but their lines of action do not lie on the same plane
B. do not meet at one point and their lines of action do not lie on the same plane
C. do not meet at one point but their lines of action lie on the same plane
D. none of the above
43. The forces which meet at one point, but their lines of action __________ on the same plane, are Known as non-coplanar concurrent forces.
B. do not lie
44. A force while acting on a body may
A. change its motion
B. balance the forces, already acting on it
C. give rise to the internal stresses in it
D. all of these
45. A screw jack used for lifting the loads is
A. a reversible machine
B. a non-reversible machine
C. an ideal machine
D. none of these
46. The wheels of a moving car possess
A. potential energy only
B. kinetic energy of translation only
C. kinetic energy of rotation only
D. kinetic energy of translation and rotation both
47. In order to determine the effects of a force, acting on a body, we must know
A. magnitude of the force
B. line of action of the force
C. nature of the force i,e. whether the force is push or pull
D. all of the above
48. The negative acceleration is called retardation.
49. The maximum displacement of a body, from its mean position, is called amplitude.
50. A lifting machine lifts a load of 1000N through a distance of 0.2 m by means of an effort of 200N through a distance of 1m. This machine is an ideal one.