Strength Of Materials MCQ Questions & Answers

51

The algebraic sum of moments of the forces forming couple about any point in their plane is

A) Equal to the moment of the couple B) Constant C) Both of above are correct D) Both of above are wrong

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Answer & Solution

Answer: Option A

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52

A force acting on a body may

A) Introduce internal stresses B) Retard its motion C) Change its motion D) All of the above

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Answer & Solution

Answer: Option D

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53

The angle which an inclined plane makes with the horizontal when a body placed on it is about to move down is known as angle of

A) Friction B) Limiting friction C) Repose D) Kinematic friction

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Answer & Solution

Answer: Option C

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54

When trying to turn a key into a lock, following is applied

A) Coplanar force B) Non-coplanar forces C) Moment D) Couple

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Answer & Solution

Answer: Option D

Solution:

Imagine you're trying to open a door with a key.
You're not just pushing or pulling straight (that would be a force).
Instead, you're twisting the key.
This twisting action is what we call a moment in engineering.
A moment is a turning effect caused by a force acting at a distance from a pivot point (in this case, the center of the lock).
It's like a force trying to rotate something.
So, the correct answer is a moment because it describes the turning action you apply to the key in the lock.
Coplanar forces act in the same plane, which isn't what happens when you turn a key.
Non-coplanar forces act in different planes, also not applicable here.
A couple is two equal and opposite parallel forces, which also doesn't represent the action of turning a key.

55

Which is the correct statement about law of polygon of forces?

A) If any number of forces acting at a point can be represented by the sides of a polygon taken in order, then the forces are in equilibrium B) If any number of forces acting at a point can be represented in direction and magnitude by the sides of a polygon, then the forces are in equilibrium C) If a polygon representing forces acting at a point is closed then forces are in equilibrium D) If any number of forces acting at a point can be represented in direction and magnitude by the sides of a polygon taken in order, then the forces are in equilibrium

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Answer & Solution

Answer: Option D

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56

The effort required to lift a load W on a screw jack with helix angle $$\alpha $$ and angle of friction $$\varphi $$ is equal to

A) $${\text{W}}\tan \left( {\alpha + \varphi } \right)$$ B) $${\text{W}}\tan \left( {\alpha - \varphi } \right)$$ C) $${\text{W}}\cos \left( {\alpha + \varphi } \right)$$ D) $${\text{W}}\sin \left( {\alpha + \varphi } \right)$$

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Answer & Solution

Answer: Option A

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57

In actual machines

A) Mechanical advantage is greater than velocity ratio B) Mechanical advantage is equal to velocity ratio C) Mechanical advantage is less than velocity ratio D) Mechanical advantage is unity

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Answer & Solution

Answer: Option C

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58

A heavy ladder resting on floor and against a vertical wall may not be in equilibrium, if

A) The floor is smooth and the wall is rough B) The floor is rough and the wall is smooth C) The floor and wall both are smooth surfaces D) The floor and wall both are rough surfaces

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Answer & Solution

Answer: Option C

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59

The C.G. of a right circular solid cone of height h lies at the following distance from the base

A) $$\frac{{\text{h}}}{2}$$ B) $$\frac{{\text{h}}}{3}$$ C) $$\frac{{\text{h}}}{6}$$ D) $$\frac{{\text{h}}}{4}$$

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Answer & Solution

Answer: Option D

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60

According to principle of moments

A) If a system of coplanar forces is in equilibrium, then their algebraic sum is zero B) If a system of coplanar forces is in equilibrium, then the algebraic sum of their moments about any point in their plane is zero C) The algebraic sum of the moments of any two forces about any point is equal to moment of the resultant about the same point D) Positive and negative couples can be balanced

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Answer & Solution

Answer: Option B

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Strength Of Materials MCQ Questions & Answers | Civil Engineering