Science - Grade 8 (C ...

Q1. Fill in the blanks.

                         i.        Friction opposes the __________ between the surfaces in contact with each other.

                        ii.        Friction depends on the ____________ of surfaces.

                       iii.        Friction produces _____________.

                       iv.        Sprinkling of powder on the carrom board ___________ friction.

                        v.        Sliding friction is __________ than the static friction.

 

Q2. True/False

                        i.        The force of friction always opposes the applied force. ________

                       ii.        On rough surfaces, there are a lesser number of irregularities. ______

                      iii.        Sliding friction is slightly smaller than the static friction. _________

                      iv.        Friction is caused by the irregularities on the two surfaces in contact. _______

                       v.        Soles of shoes wear out due to gravity. ________

 

Q3. Which force helps things to move and stop?

 

Q4. What enables a ladder to lean against the wall?

 

Q5. Name two common lubricants.

 

Q6. Mention one simple method of reducing friction between two surfaces.

 

Q7. What is drag?

 

Q8. Which type of surface produces less friction?

 

Q9. Why the soles of our shoes wear out gradually?

 

Q10. Which type of surface produces more friction?

 

Q11. Why ball bearings are used in machines?

Or

What is the purpose of using ball bearing in machine?

 

Q12. Write any two machines in which ball bearings are used.

 

Q13. What makes the steps of foot over-bridges at Railway Stations to wear out slowly?

 

Q14. What are lubricants?

 

Q15. Why do we sprinkle fine powder on the carrom board?

 

Q16. Name the force responsible for wearing out of car tyres.

 

Q17. What is the direction of force of friction acting on a moving object?

Or

What is the direction of force of friction?

 

Q18. Which force always opposes motion?

Or

What is the force that always opposes motion?

 

Q19. What is done to increase friction between the tyres and road?

 

Q20. When does static friction come into play?

 

Q21. When does sliding friction come into play?

 

Q22. Why is the surface of a slide polished to make it smooth?

 

Q23. Why do kabaddi players rub their hands with dry soil?