# Machine Design Questions and Answers – Static & Dynamic Load Carrying Capacity

This set of Basic Machine Design Questions & Answers focuses on “Static & Dynamic Load Carrying Capacity”.

1. Static load is defined as the load acting on the bearing when shaft is _____
a) Stationary
b) Rotating at rpm<10
c) Rotating at rpm<5
d) None of the listed

Explanation: As name suggests, static load means load during stationary position of the shaft.

2. A total permanent deformation of 0.0001 of the ball diameter is taken for considering static load capacity of the shaft.
a) True
b) False

Explanation: Permissible magnitude of deformation is set as per the experimental data.

3. Stribeck equation gives dynamic load capacity of the bearing.
a) True
b) False

Explanation: It gives static load capacity of the bearing.

4. Which of the following is expression for stribeck equation?(Number of balls=z)?
a) C=kd²z/5
b) C=kd²z/15
c) C=kd²z/10
d) None of the listed

Explanation: C=(1/5)zP and P=kd².

5. The life of an individual ball bearing is the time period for which it works without any signs of failures.
a) True
b) False

Explanation: It is measured by number of revolutions and not by time.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

6. For majority of bearings, actual life is considerably greater than rated life.
a) True
b) False

Explanation: Stastically it has been proved that life which 50% of a group of bearings will exceed is approximately five times rating of rated life.

7. The dynamic load carrying capacity of a bearing is defined as the radial load in radial bearings that can be carried for a minimum life of 1000 revolutions.
a) True
b) False

Explanation: It is for 1 million revolutions.

8. In the expression of dynamic load capacity P=XVF(r) + YF(a), V stands for ?
a) Race rotation factor
c) Thrust factor
d) None of the listed

Explanation: It represent race rotation factor which depends upon whether inner race is rotating or outer race.

9. Calculate the bearing life if expected life for 90% bearings is 9000h and shaft is rotating at 1500rpm.
a) 850 million rev
b) 810 million rev
c) 810 h
d) 850h

Explanation: L=60x1500x9000/10⁶ million rev.

10. The bearing is subjected to a radial load of 4000N. Expected life for 90% bearings is 9000h and shaft is rotating at 1500rpm. Calculate the dynamic load capacity.
a) 42.21kN
b) 37.29kN
c) 26.33kN
d) 35.22kN

Explanation: C=4000x(810)⅓.

11. A rolling contact bearing is specified as X307. Calculate the bearing diameter.
a) 35mm
b) 28mm
c) 21mm
d) 7mm

Explanation: Diameter=5 times the last two digits.

12. A rolling contact bearing is specified as X307. Determine the series.
a) Extra light series
b) Light series
c) Medium series
d) Heavy series

Explanation: 1- Extra light series,2-Light series,3-Medium series,4-heavy series.

13. Needles bearing consist of rollers of small diameter and very small length.
a) True
b) False

Explanation: Also called as quill bearings, they consist of small diameter and comparatively longer b=rollers.

14. Extreme pressure causes ______ wear in the bearing parts.
a) Abrasive
b) Corrosive
c) Pitting
d) All of the mentioned

Explanation: Extreme pressure elements in EP additives are added in lubricating oils.

15. Scoring is a ________ phenomenon.
a) Stick-slip
b) Fracture
c) Fatigue
d) In-out

Explanation: Alternative welding and shearing takes place.

Sanfoundry Global Education & Learning Series – Machine Design.
To practice basic questions on all areas of Machine Design, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]