# Engineering Mechanics – Section 6

21. The cartesian equation of trajectory is(where u = Velocity of projection, α = Angle of projection, and xy = 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)

Correct Answer: C. 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

Correct Answer: A. √3. W (tensile) and 2W (compressive)

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-m2
B. kg-m-s2
C. kg/m2
D. m4

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. ml2/4
B. ml2/ 6
C. ml2/8
D. ml2/12

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

A. mv2
B. mgv2
C. 0.5 mv2
D. 0.5 mgv2

28. The unit of angular velocity is

A. m/min
C. revolutions/min
D. both (B) and (C)
E. none of these

Correct Answer: D. both (B) and (C)

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