Engineering Mechanics – Section 2

31. Which of the following statement is correct?

A. The kinetic energy of a body during impact remains constant.
B. The kinetic energy of a body before impact is equal to the kinetic energy of a body after impact.
C. The kinetic energy of a body before impact is less than the kinetic energy of a body after impact.
D. The kinetic energy of a body before impact is more than the kinetic energy of a body after impact.

Correct Answer: D. The kinetic energy of a body before impact is more than the kinetic energy of a body after impact.

32. The maximum efficiency of a screw jack is

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Correct Answer: Option A

33. In a framed structure, as shown in the below figure, the force in the member AC is numerically equal to the force in member BC.

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A. Correct
B. Incorrect

Correct Answer: A. Correct

34. The force which acts along the radius of a circle and directed towards the center of the circle is known as centripetal force.

A. True
B. False

Correct Answer: A. True

35. Moment of inertia of a triangular section of the base (b) and height (h) about an axis through its base, is

A. bh3/4
B. bh3/8
C. bh3/ 12
D. bh3/ 36

Correct Answer: C. bh3/ 12

36. Concurrent forces are those forces whose lines of action

A. lie on the same line
B. meet at one point
C. meet on the same plane
D. none of these

Correct Answer: B. meet at one point

37. The tension in the cable supporting a lift is more when the lift is moving __________ with an acceleration.

A. upwards
B. downwards

Correct Answer: A. upwards

38. According to the law of moments, if a number of coplanar forces acting on a particle are in equilibrium, then

A. their algebraic sum is zero
B. their lines of action are at equal distances
C. the algebraic sum of their moments about any point in their plane is zero
D. the algebraic sum of their moments about any point is equal to the moment of their resultant force about the same point.

Correct Answer: C. the algebraic sum of their moments about any point in their plane is zero

39. If u1 and u2 are the velocities of two moving bodies in the same direction before impact and v1 and v2 are their velocities after impact, then the coefficient of restitution is given by

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Correct Answer: Option B

40. Two bodies of masses m1 and m2 are hung from the ends of a rope, passing over a frictionless pulley as shown in the figure below. The acceleration of the string will be

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Correct Answer: Option A

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