This set of Mechatronics online quiz focuses on “Mechanical Actuating Systems – Preloading”.

1. What is the type of preload called when a bearing experiences a stress due to negative clearance?

Explanation: When a bearing experiences a stress due to negative clearance then it is a type of bearing preload. These types of preload increases the bearing rigidity and helps in maintaining actual radial and axial position for displacement.

2. What is the strain on an object, when a force of 3 Newton is applied on it and it expands the length of the object from 4cm to 6 cm?
a) 2
b) 0.5
c) 1
d) 8

Explanation: Given:-
Force applied=3 N
Original length(o)=4cm
New length=6 cm
Extended length(e)=New length-Original length
Extended length(e)=6-4=>2cm
Strain (s) = Extended length(e)/Original length(o)
Strain (s)=2cm/4cm=>0.5.

3. What is the ratio of stress to strain called?
a) Youngs Modulus
b) Bulks Modulus
c) Modulus of elasticity
d) Modulus of rigidity

Explanation: The ratio of stress to strain is called as Youngs Modulus. It is a mechanical property that measures the stiffness of a body. It establishes a relationship between stress and strain of a body. The youngs modulus graph or the stress-strain graph of a body showing elastic property is a straight line which shows the stress is proportional to strain.

4. What is the unit of stress?
a) Meter
b) Newton/Meter
c) Newton
d) Pascal

Explanation: The unit of stress is Pascal. Stress is defined as the ratio of internal force of a material to resist deformation to the area of impact. Mathematically this gives out the unit as Newton/meter2 which is also termed as “Pascal”.

5. Pressure and stress are same as both are defined as force per unit area.
a) True
b) False

Explanation: Pressure and stress are not same even if both are defined as force per unit area. The word “force” in pressure is the external force applied on a body, whereas “force” in the definition of stress refers to the internal force of a material to resist deformation.

6. Stress on a body occurs only when compressive force act on it.
a) True
b) False

Explanation: Stress on a body occurs not only when compressive force act on it; but also when sheer or expanding forces are applied. Stress occurs on a body when any force is applied irrespective of the direction of the force.

7. What is the unit of strain?
a) Meter
b) Newton/Meter
c) Newton/Meter2
d) No unit

Explanation: Strain has no unit. It is so because it is the ratio of two lengths. Strain is defines as the ratio of extended length of an object to its original length. Since both numerator and denominator have the unit of length, therefore they cancel out each other and thus strain has no unit.

8. What is the strain on a hook of a hanger, when its length expands from 5cm to 6 cm due to a hanging load?
a) 0.2
b) 0.5
c) 1.2
d) 0.3334

Explanation: Given:-
Original length(o)=5cm
New length=6cm
Extended length(e)=New length-Original length
Extended length(e)=6-5=>1cm
Strain (s) = Extended length(e)/Original length(o)
Strain (s)=1cm/5cm=>0.2.

9. What is the value of stress that occurs on an object when a force of 5 Newton is applied perpendicularly to an area of 1meter2?
a) 2 Newton/meter2
b) 5 Newton/meter2
c) 1.2 Newton/meter2
d) 1 Newton/meter2

Explanation: Given:-
Force applied=5 N
Area of impact=1meter2
Stress (S) = Force applied/Area of impact
Stress (S) = 5 N/1meter 2=>5 N/meter2.

10. What is the strain on a hanging load, when a force of 1 Newton is applied on it and it expands the length of the object from 9cm to 12 cm?
a) 2
b) 0.5
c) 1.2
d) 0.3334

Explanation: Given:-
Force applied=1 N
Original length(o)=9cm
New length=12 cm
Extended length(e)=New length-Original length
Extended length(e)=12-9=>3cm
Strain (s) = Extended length(e)/Original length(o)
Strain (s)=3cm/9cm=>0.3334.

11. Preloads can avoid resonance due to external disturbances.
a) True
b) False

Explanation: Preloads can avoid resonance due to external disturbances. These preloads can avoid harmful or the damage causing resonance by tensioning and increasing the natural frequency of the structure.

12. Pressure and stress both have same unit (i.e) “Pascal”.
a) True
b) False

Explanation: Pressure and stress both have same unit (i.e) “Pascal”. The word “force” in pressure is the external force applied on a body, whereas “force” in the definition of stress refers to the internal force of a material to resist deformation. But mathematically they have same formula (i.e) Force/unit area which gives their units as Newton/meter2 or “Pascal”.

13. Sheer stress occurs when a body expands due to external force.
a) True
b) False

Explanation: Sheer stress does not occur when a body expands due to external force. When a body expands due to external force it undergoes tensile stress. Sheer stress occurs when there is slippage along the plane parallel to the direction of imposed stress and a deformation in the shape of the object occurs.

14. What is the nature of the stress-strain graph of an elastic body?
a) Asymptotic
b) Linear
c) Parabolic
d) Non-Linear

Explanation: The nature of the stress-strain graph of an elastic body is Linear. The youngs modulus graph or the stress-strain graph of a body showing elastic property is a straight line which shows the stress is proportional to strain.

15. What is the strain on a hanging load, when a force of 5 Newton is applied on it and it expands the length of the object from 8cm to 12 cm?
a) 2
b) 0.5
c) 1
d) 8

Explanation: Given:
Force applied=5 N
Original length(o)=8cm
New length=12 cm
Extended length(e)=New length-Original length
Extended length(e)=12-8=>4cm
Strain (s) = Extended length(e)/Original length(o)
Strain (s)=4cm/8cm=>0.5.

Sanfoundry Global Education & Learning Series – Mechatronics.

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