Q1) Write true or false for each statement :
(a) The frictional force acts in the direction of motion of the body.
(b) The unit of weight is kilogram.
(c) A force can change the direction of motion of a moving body.
(d) A force increases the mass of the body when applied on it.
(e) The force of friction is always disadvantageous.
(f) The sliding friction is more than the rolling friction.
(g) Liquids offer more friction than the gases.
(h) A wet oily road offers more friction than a dry rough road.
Q2 Fill in the blanks
(a) Force is applied as ______or ______ .
(b) On squeezing a gum tube, its ______ changes.
(c) On pulling a string, its ______ increases.
(d) A moving football when kicked, its ______ __________ changes.
(e) On applying brakes on a moving car, its speed ________.
(f) We use ball bearings to ______ friction.
(g) Friction ______ the motion.
(h) Lubricants are used to _________ friction.
(i) _________ causes wear and tear of moving parts of a machine.
Q3) Match the following columns :
|Column A||Column B|
|(a) Non contact force||(i) repel|
|(b) Like poles||(ii) kg|
|(c) Contact force||(iii) Gravitional force|
|(d) Mass||(iv) wear and tear|
|(e) Weight||(v) force of friction|
|(f) Friction||(vi) kgf|
Q4) Select the correct alternative :
(a) A body falls downwards because of
(b) A force does not change
State of motion
(c) A force to be expressed correctly requires
Only the magnitude
Only the direction
Both the magnitude and direction
None of the above.
Acts in the direction of motion
Is always a nuisance
(e) Friction is reduced by
Making the surfaces wet
Making the surfaces dry
Making the surfaces rough
Sprinkling sand on the surface.
Causes wear and tear
Stops a moving body
Has all the above disadvantages
(g) Friction is increased if
Oil is sprayed
The surfaces are made wet
The surfaces are made dry
The surfaces are polished
Q7) Give one example each to indicate that the application of a force :
slows down motion
changes the direction of motion
deforms a body
Q8) State the effect produced by a force in the following cases :
(a) The sling of a rubber catapult is stretched.
(b) A man pushes a heavy cart.
(c) A player uses his stick to deflect the ball.
(d) A cyclist applies brakes.
(e) A spring is compressed.
Q10) Name the type of force which acts in the following cases :
(a) A coolie lifts a luggage
(b) A bicycle comes to rest slowly when the cyclist stops pedalling
(c) A stone falls from a roof
(d) A comb rubbed with silk attracts the bits of paper
(e) A string hangs with a load
(f) A horse moves a cart
(g) A magnet attracts an iron pin
(h) A boy opens the door
(i) An apple falls from a tree
(j) A man rows a boat
Q17) In which case will there be more friction between the truck and the road : when the truck is empty or when it is loaded ?
Q21) When you apply the brakes, the bicycle stops and the rim of the wheel becomes hot. Explain the reason.
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