# Machine Kinematics Questions and Answers – Systems of Gear Teeth

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This set of Machine Kinematics Multiple Choice Questions & Answers (MCQs) focuses on “Systems of Gear Teeth”.

1. The face of the tooth is the
a) surface of the top of tooth
b) surface of tooth above the pitch surface
c) width of tooth below the pitch surface
d) width of tooth measured along the pitch circle

Explanation: Face of tooth is the surface of the gear tooth above the pitch surface.
Flank of tooth is the surface of the gear tooth below the pitch surface.

2. The flank of the tooth is the surface of the tooth _____________ the pitch surface.
a) above
b) below
c) on
d) none of the mentioned

Explanation: Face of tooth is the surface of the gear tooth above the pitch surface.
Flank of tooth is the surface of the gear tooth below the pitch surface.

3. The ratio of the number of teeth to the pitch circle diameter in millimeters, is called
a) circular pitch
b) diametral pitch
c) module
d) none of the mentioned

Explanation: Diametral pitch is the ratio of number of teeth to the pitch circle diameter in millimetres.
Circular pitch is the distance measured on the circumference of the pitch circle from a point of one tooth to the corresponding point on the next tooth.
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4. The ratio of the pitch circle diameter in millimeters to the number of teeth, is called circular pitch.
a) True
b) False

Explanation: Diametral pitch is the ratio of number of teeth to the pitch circle diameter in millimetres.
Circular pitch is the distance measured on the circumference of the pitch circle from a point of one tooth to the corresponding point on the next tooth.

5. The product of the diametral pitch and circular pitch is equal to
a) 1
b) 1/п
c) п
d) 2п

Explanation: None.

6. The product of the diametral pitch and module is equal to one.
a) True
b) False

Explanation: None.

7. The module is the reciprocal of diametral pitch.
a) True
b) False

Explanation: Diametral pitch is the ratio of number of teeth to the pitch circle diameter in millimetres.
Module is the ratio of the pitch circle diameter in millimeters to the number of teeth.

8. The dedendum circle diameter is equal to
a) pitch circle dia. x cosɸ
b) addendum circle dia. x cosɸ
c) clearance circle dia. x cosɸ
d) pitch circle dia. x sinɸ

Explanation: It is the circle drawn through the bottom of the teeth. It is also called root circle.
Root circle diameter = Pitch circle diameter × cos φ, where φ is the pressure angle.

9. The contact ratio is the ratio of
a) length of pair of contact to the circular pitch
b) length of arc of contact to the circular pitch
c) length of arc of approach to the circular pitch
d) length of arc of recess to the circular pitch

Explanation: The ratio of the length of arc of contact to the circular pitch is known as contact ratio i.e. number of pairs of teeth in contact.

10. According to law of gearing, the common normal at the point of contact between a pair of teeth must always pass through the pitch point.
a) True
b) False

Explanation: None.

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