Q 1 – Which of the following is not a smooth surface?
(a) Surface of wet soap
(b) Surface of tyres
(c) Glazed tiles
(d) Surface of mirror
Q 2 – If we apply oil on door hinges, the friction will
(a) increase
(b) decrease
(c) disappear altogether
(d) will remain unchanged
Q 3 – Lubricant
(a) reduce friction
(b) increase friction
(c) both (a) and (b)
(d) none of these
Q 4 – Force of friction depends on
(a) roughness of surface
(b) smoothness of surface
(c) inclination of surface
(d) all of these
Q 5 – Which is a streamlined object?
(a) Boats
(b) Aeroplanes
(c) Ships
(d) All of these
Q 6 – It is difficult to walk on an oily floor because
(a) Floor gets spoiled
(b) There is more resistance
(c) Force of friction is high
(d) Force of friction is very less
Q 7 – Spring balance is a device used for measuring the _____________ acting on an object.
(a) mass
(b) pressure
(c) force
(d) None of the above
Q 8 – Tyres are treaded to
(a) look good
(b) Increase friction
(c) increase its longivity
(d) increase weight of the tyre
Q 9 – Sliding friction is _________ than / to rolling friction
(a) smaller
(b) greater
(c) equal
(d) None of the above
Q 10 – Talcum powder should not be spilled on the Floor of room because:
(a) it will stain the Floor
(b) it may cause us to slip and fall
(c) it is messy
(d) none of these
Q 11 – Fill in the blanks
- Sliding friction is ___________ than static friction.
- Friction can be reduced by using ___________.
- Friction can be increased by making surface ___________.
- Rolling friction is ___________ than sliding and static friction.
- Friction due to fluid is also called ___________.
- Bodies of birds, fishes and ships are ___________.
Q 12 – True or false
- Friction is always useful to us.
- Fluids are only liquids.
- Friction is less for smooth surfaces.
- A soapy floor is slippery due to increased friction.
- Friction always works in opposite direction to the relative motion
Q 13 – If we push the book on the table, it stops after sometime. Why?
Q 14 – Why is it easier for the fish to swim in water?
Q 15 – What is a spring balance?
Q 16 – How does the friction depend on the nature of the surface?
Q 17 – When the two surfaces are pressed harder, friction increases. Explain why?
Q 18 – Why is it easier to move the box already in motion than to get it started?
or
The sliding friction is slightly smaller than the static friction. Explain why?
Q 19 – Why are lubricants applied between the moving part of a machine?
Q 20 – People often rub their hands in winter. Why?
Q 21 – In some cases, we deliberately increase friction. Explain why?
Q 22 – What are the various types of friction? Explain.
Q 23 – What do you mean by fluid friction? How can fluid friction be reduced?
Q 24 – Write advantages and disadvantages of friction.
Q 25 – Ram and Shyam while returning from school saw a labour pushing hard to move a heavy box. Ram immediately ran to him and started helping him in pushing the box whereas Shyam brought two iron bars and asked the labour to put them below the box and then to push the box.
- What are the factors that affect friction?
- Who will help the labour more-Ram or Shyam? How?
- What values of Ram and Shyam are shown here?
Q 26 – Visit a shop which sells sports shoes. Observe the soles of shoes meant for various sports. Describe your observations?