Class 8 Science Chapter 9 MCQ

That car travels a larger distance on the “wet marble floor” and a shortest distance will cover in “towel”. And “dry marble floor” resist less friction force than “newspaper”. Hence, force of friction acting on the car on different surfaces in increasing order will be option [A] as “wet marble floor, dry marble floor, newspaper and then towel”.

Force of friction acts in solids, liquids and gases and opposes the motion with respect to each other.

We know that friction force acts in an opposite direction to the direction in which an object moves. The maximum frictional force present between two objects is static friction. And sliding friction is smaller than static friction. And rolling friction is much less than sliding friction. Hence, your answer will be option [C].

Stone will be more suitable because it will exert greater reaction and hence greater friction force which sharpen the blade of a knife easily by rubbing.

It will go farthest on the surface having least frictional force i.e., the polished marble surface.

The friction between two surfaces depends on two factors first is, the nature of the two surfaces or smoothness or roughness of the two surfaces and second is, the force with which two surfaces are pressed together or weight. But amount of surface area of the two objects which is in contact with each other does not depend on the friction force.

We know that friction force acts in an opposite direction to the direction in which an object moves. The maximum frictional force present between two objects is static friction. And sliding friction is smaller than static friction. And rolling friction is much less than sliding friction. The static friction is always greater than sliding friction.

Talcum powder reduces friction force and the ball will cover longer distance.

There are many advantages and disadvantages of friction force. Here, all are the advantages mentioned in all options, except one i.e., option [C]. Friction enables rubber pads to be rubbed off, the tyres of vehicles wear out gradually, soles of our shoes tear out, brake pads of vehicles rubbed off also.

We know that friction force acts in an opposite direction to the direction in which an object moves. The maximum frictional force present between two objects is static friction. And sliding friction is smaller than static friction. And rolling friction is much less than sliding friction. The relationship between the three types of friction is: The static friction > Sliding Friction > Rolling friction. Thus, the rolling friction will be less than 20N.

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

The friction between two surfaces depends on two factors first is, the nature of the two surfaces or smoothness or roughness of the two surfaces and second is, the force with which two surfaces are pressed together or weight. As the roughness of the surface increases, the friction increases. Here, glazed paper, glass table top and aluminium frame produces less friction than “sand paper”. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

Friction is caused by the interlocking of irregularities in the surfaces of the two objects which are in contact with each other. Sliding friction is between two objects when one or both are sliding against each other. In this case, the book is sliding down the titled table. So, the motion is directed downwards. So, the friction will act on the book in the direction opposite to movement. So, friction will act upwards. Sliding friction is less than static friction, so when the table is titled, the book starts to slide. Here, your answer will be option [B].

Here, all the statements are correct. Hence, your answer will be option [D].

A body shape which offers very little resistance to the flow of a fluid around it, is called streamlined shape.

Remember, friction enables a ladder to be leaned against the wall and not slip down to the floor. The irregularities capture the both ends of ladders.

Here, all the statements are correct. Hence, your answer will be option [D].

Mustard oil reduces the friction on his hands. So, Glass tumbler will be most difficult to handle. Rest of all have much irregularities to hold. And glass has very smooth surface. Hence, your answer will be option [C].

Here, all the statements are correct. Hence, your answer will be option [D].

Wrapping of jute clothes make the surface of brick more-rough due to which the friction with floor increases.

Here, all the statements are correct. Hence, your answer will be option [D].