Interactive Graded Test on Sliding Friction

This is an interactive test that will automatically check your answers and calculate your grade. This test has 20 questions and is based on material from the Friction section of lessons:

Friction

• Resistive Force of Friction
• Uses of Friction
• Causes of Friction

Sliding friction

• Standard Friction Equation
• Changing Sliding Friction on Hard Surfaces
• Coefficient of Friction Values for Clean Surfaces
• Coefficient of Friction Values for Greased Surfaces

It is a good idea to study these lessons before taking this graded test.

(Also see Interactive Graded Test on Rolling Friction.)

QUIZ

Self-check your understanding

1. Why is it harder to start to slide a heavy box across the floor than to keep it sliding?

   Static friction is greater than kinetic frictionThat is correct.Kinetic friction is greater than the static frictionGood try, but not right. Select another answer.Sliding friction is less than rolling frictionSorry, not correct. Try another button.

2. What is an advantage of using rollers instead of sliding an object?

   Rollers are much less expensiveGood try, but not right. Select another answer.Rolling friction is much less than sliding frictionThat is correct.Rolling friction has the advantage of being greater than sliding frictionSorry, not correct. Try another button.

3. Why is it easier to move water through a hose than grease?

   Since grease is slippery, it actually moves easier than waterGood try, but not right. Select another answer.Water has less viscosity than grease and thus less fluid frictionThat is correct.Because you would never move grease through a hose in the first placeSorry, not correct. Try another button.

4. Is friction required when you are sleeping?

   No, because you are not awake or doing anythingGood try, but not right. Select another answer.Scientists are not certain since the person is not awakeSorry, not correct. Try another button.Yes, because without friction you could not roll overThat is correct.

5. What is the most common way to reduce friction that is hindering motion?

   LubricationThat is correct.Warning signsGood try, but not right. Select another answer.Eliminate the motionSorry, not correct. Try another button.

6. Do you want to increase or decrease friction when riding a bicycle?

   Increase, because you don't want to go too fastGood try, but not right. Select another answer.Both, because you want to be able to stop but yet peddle easilyThat is correct.Decrease, because you don't want to peddle too hardSorry, not correct. Try another button.

7. How does surface roughness affect friction?

   The tiny bumps make sliding motion more difficultThat is correct.Roughness prevents any motionGood try, but not right. Select another answer.Surface roughens causes molecular effectsSorry, not correct. Try another button.

8. What is the major cause of friction when sliding a heavy box through mud?

   Deformation or plowing frictionThat is correct.Molecular attraction of the mud to the box materialGood try, but not right. Select another answer.Kinetic or moving frictionSorry, not correct. Try another button.

9. Why does double-sided tape prevent an object from sliding?

   The tape has a large static coefficient of friction on both sidesThat is correct.The tape deforms both objectsGood try, but not right. Select another answer.The tape actually helps slidingSorry, not correct. Try another button.

10. How are the equations for static and kinetic friction different?

    Same equation with different values of the coefficient of frictionThat is correct.Kinetic friction has an area componentGood try, but not right. Select another answer.Static friction does not use the coefficient of frictionSorry, not correct. Try another button.

11. As the angle of an incline increases, what happens to the normal force?

    It increases until it gets to infinityGood try, but not right. Select another answer.Nothing, because normal force has nothing to do with the inclineSorry, not correct. Try another button.It decreases until it reaches zeroThat is correct.

12. Once you found the friction and normal forces, how do you determine the coefficient of friction?

    Multiply friction force times normal forceGood try, but not right. Select another answer.Divide friction force by normal forceThat is correct.Add friction force to normal forceSorry, not correct. Try another button.

13. What happens as you reduce surface roughness?

    The coefficient of friction increases until the surfaces are so smooth that it then decreasesGood try, but not right. Select another answer.The coefficient of friction decreases until the surfaces are so smooth that it then increasesThat is correct.The coefficient of friction decreases until the surfaces are so smooth that it it becomes zeroSorry, not correct. Try another button.

14. Does a lubricant always reduce friction?

    Yes, a lubricant will always reduce friction to a very small forceGood try, but not right. Select another answer.No one is really sure, because all possibilities have never been triedSorry, not correct. Try another button.No, a heavy grease lubricant may increase friction in some applicationsThat is correct.

15. What happens when you pull slightly upward on a rope as you slide an object along the floor?

    The upward pull reduces the normal force and thus reduces the frictionThat is correct.The upward pull pivots the object against the floor, making it harder to pullGood try, but not right. Select another answer.The object will tip overSorry, not correct. Try another button.

16. Should surface roughness of the materials be indicated in coefficient tables?

    Yes, because surface roughness can affect the friction coefficientThat is correct.No, because we can assume the material is relatively smoothGood try, but not right. Select another answer.Engineers aren't sure if surface roughness is a factor in frictionSorry, not correct. Try another button.

17. Why should environmental testing conditions be noted?

    They are only important to control pollutionGood try, but not right. Select another answer.A humid testing environment could reduce the friction valuesThat is correct.To satisfy the Environmental Protection Act (EPA)Sorry, not correct. Try another button.

18. What is a likely reason some readings have a range of coefficients?

    No one is sure why that happenedGood try, but not right. Select another answer.Measurements were made under different conditionsThat is correct.The coefficient of friction is independent of materials usedSorry, not correct. Try another button.

19. Should the type and amount of grease be stated in listing coefficient?

    No, because only surface roughness determines frictionGood try, but not right. Select another answer.No one is sure whether the type makes any differenceSorry, not correct. Try another button.Yes, because lubrication varies greatly with materialThat is correct.

20. When should you make your own friction measurements?

    When the exact amount of friction needs to be knownThat is correct.When the normal force variesGood try, but not right. Select another answer.You do not need to use anything but a table of valuesSorry, not correct. Try another button.

Pick an answer to see instant feedback. Re-read the lesson if you miss one.

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Don’t be held back by friction

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