Engineering Mechanics

Question 1

1. Engineering mechanics is the study of ___.
   A. Forces and their effects on bodies B. Materials behavior C. Structures only D. Fluids in motion

Answer 1

✅ Answer: A – Forces and their effects on bodies
Basis of statics and dynamics.

Question 2

2. Statics deals with ___.
   A. Accelerating bodies B. Bodies at rest or constant velocity C. Rotating systems D. Elastic deformation

Answer 2

✅ Answer: B – Rest or constant velocity
ΣF = 0, ΣM = 0.

Question 3

3. A body is in equilibrium if ___.
   A. ΣF = 0 only B. ΣM = 0 only C. ΣF = 0 and ΣM = 0 D. Zero acceleration only

Answer 3

✅ Answer: C – Both force and moment balance
No linear or rotational motion.

Question 4

4. The moment of a force about a point is ___.
   A. F × r B. r × F C. r/F D. F/r

Answer 4

✅ Answer: B – Vector cross product (M = r × F)
Direction given by right-hand rule.

Question 5

5. Unit of moment (torque) is ___.
   A. N B. N/m C. N·m D. N/m²

Answer 5

✅ Answer: C – Newton-meter
Force × distance.

Question 6

6. The resultant of two concurrent forces P and Q making angle θ is ___.
   A. √(P² + Q² + 2PQcosθ) B. P + Qcosθ C. P – Qsinθ D. PQsinθ

Answer 6

✅ Answer: A – Law of cosines
Vector addition formula.

Question 7

7. The parallelogram law of forces states that ___.
   A. Resultant is sum of magnitudes B. Diagonal represents resultant C. Triangle forms equilibrium D. None

Answer 7

✅ Answer: B – Diagonal represents resultant
Constructed between two concurrent forces.

Question 8

8. If two equal forces act at 120°, resultant = ?
   A. Equal to one of them B. Twice one C. √3 times one D. Half one

Answer 8

✅ Answer: A – Equal to one force
R = √(F²+F²+2F²cos120) = F.

Question 9

9. A system of coplanar parallel forces has ___.
   A. Resultant equal to algebraic sum of forces B. Zero moment C. No equilibrium D. None

Answer 9

✅ Answer: A – Sum of vertical/horizontal components
Resultant equals net vertical/horizontal.

Question 10

10. Moment of couple = ___.
    A. Force × arm distance B. Sum of forces C. Zero D. F × cosθ

Answer 10

✅ Answer: A – F × arm
Independent of reference point.

Question 11

11. A couple produces ___.
    A. Linear motion B. Pure rotation C. Translation D. Deformation

Answer 11

✅ Answer: B – Pure rotation
Equal and opposite forces separated by distance.

Question 12

12. The condition for a three-force body in equilibrium is ___.
    A. All forces concurrent or parallel B. Random forces C. Coplanar nonconcurrent D. 90° between any two

Answer 12

✅ Answer: A – Concurrent or parallel
All forces must intersect at one point or be parallel.

Question 13

13. The centroid of a triangle is located at ___.
    A. ½ of base B. ⅓ of height from base C. ⅔ of height from base D. ¼ of base

Answer 13

✅ Answer: B – ⅓ of height from base
Measured along median.

Question 14

14. The centroid of a semicircle from the base = ___.
    A. 0.424r B. 0.5r C. 0.636r D. r

Answer 14

✅ Answer: A – 0.424r
From the flat base along axis of symmetry.

Question 15

15. Moment of inertia of a rectangle (base b, height h) about centroidal axis = ___.
    A. bh³/12 B. bh²/12 C. bh³/3 D. bh²/3

Answer 15

✅ Answer: A – I = bh³/12
Fundamental section property.

Question 16

16. Parallel axis theorem: ( I = I_G + Ad² ).
    Here d = ___.
    A. Distance between centroids of areas B. Distance from neutral axis to base C. Moment arm D. None

Answer 16

✅ Answer: A – Distance between axes
Used to shift inertia to new axis.

Question 17

17. Frictional force always acts ___.
    A. Perpendicular to surface B. Along direction of motion C. Opposite to relative motion D. Parallel to motion

Answer 17

✅ Answer: C – Opposite to relative motion
Resists sliding.

Question 18

18. Limiting friction = μN means ___.
    A. Friction before motion begins B. Friction after motion starts C. Average D. None

Answer 18

✅ Answer: A – Maximum static friction
Transition point from rest to motion.

Question 19

19. Angle of friction (φ) is defined by ___.
    A. tanφ = μ B. sinφ = μ C. cosφ = μ D. φ = μ²

Answer 19

✅ Answer: A – tanφ = μ
Geometric relation between N and F.

Question 20

20. The work done by a constant force F through distance s at angle θ = ___.
    A. Fs cosθ B. F/s C. F + s D. Fs sinθ

Answer 20

✅ Answer: A – W = Fs cosθ
Component of force in motion direction.

Question 21

21. Kinetic energy (K.E.) = ___.
    A. ½mv² B. mgh C. F×d D. mva

Answer 21

✅ Answer: A – ½mv²
Energy due to motion.

Question 22

22. Potential energy (P.E.) = ___.
    A. ½mv² B. mgh C. F×d D. ½kx²

Answer 22

✅ Answer: B – mgh
Energy due to position.

Question 23

23. Work–Energy Principle:
    A. Work = Energy loss B. Work done = ΔK.E. C. Work = Force × Mass D. None

Answer 23

✅ Answer: B – Work = Change in kinetic energy
Basis of energy methods.

Question 24

24. Impulse–Momentum equation:
    A. F = ma B. Ft = Δ(mv) C. F = Δp/t D. v = u + at

Answer 24

✅ Answer: B – Ft = Δ(mv)
Force-time product equals momentum change.

Question 25

25. A projectile’s horizontal range ( R = \frac{v²\sin2θ}{g} ). For maximum range, θ = ___. A. 30° B. 45° C. 60° D. 90°

Answer 25

✅ Answer: B – 45° Range max at sin2θ = 1.