21. The cartesian equation of trajectory is(where *u* = Velocity of projection, α = Angle of projection, and *x*, *y* = Co-ordinates of any point on the trajectory after *t* seconds.)

A. y = (gx²/2u² cos²α) + x. tanα

B. y = (gx²/2u² cos²α) – x. tanα

C. y = x. tanα – (gx²/2u² cos²α)

D. y = x. tanα + (gx²/2u² cos²α)

22. In collision of elastic bodies, the coefficient of restitution is the ratio of the relative velocity after impact to the relative velocity before impact.

A. True

B. False

23. In a framed structure, as shown in the below figure, the forces in the members *AB* and *BC* are respectively

A. √3. W (tensile) and 2W (compressive)

B. 2W (tensile) and √3. W (compressive)

C. 2√3. W (tensile) and 2√3. W (compressive)

D. None of the above

24. The acceleration of a particle moving with simple harmonic motion is proportional to the displacement of the particle from the mean position.

A. True

B. False

25. The unit of moment of inertia of an area is

A. kg-m^{2}

B. kg-m-s^{2}

C. kg/m^{2}

D. m^{4}

26. The moment of inertia of a thin rod of mass *m* and length *l*, about an axis through its center of gravity and perpendicular to its length is

A. *ml*^{2}/4

B. *ml*^{2}/ 6

C. *ml*^{2}/8

D. *ml*^{2}/12

27. When a body of mass *m* attains a velocity *v* from rest in time *t*, then the kinetic energy of translation is

A. *mv*^{2}

B. *mgv*^{2}

C. 0.5 *mv*^{2}

D. 0.5 *mgv*^{2}

28. The unit of angular velocity is

A. m/min

B. rad/s

C. revolutions/min

D. both (B) and (C)

E. none of these

29. If a number of forces are acting at a point, their resultant is given by

30. A force acting in the opposite direction to the motion of the body is called force of friction.

A. Agree

B. Disagree