Surface Irregularities

Q.

device used to measure friction

Q. 33.A block is placed on a rough horizontal surface . the minimum force required to slide the block is (u is coefficient of friction between the contacting surface)

Q.

How does friction depends on the nature of the surfaces in contact??

Q. How does friction arise between two surfaces in contact?

Q.

How does the friction depend on the nature of the surface?

Q. The friction between the moving parts of a machine can be reduced by using between its parts.

1. iron dust
2. sand
3. lubricants

Q.

The friction between moving parts of machinery can be reduced by applying a _________.

Q.

Friction is dependent on the shape and area of the surface in contact.

1. True
2. False

Q. A block is sliding with a constant speed. If the speed ​of the block is doubled, what change will you observe in the sliding friction and drag respectively?

Q.

Why friction even exists between two smooth surfaces? Why force of friction is greater if a rough surface is involved?
[3 MARKS]

Q. Fast-moving vehicles are designed to have streamlined shapes to reduce the drag.

1. True
2. False

Q. This section contains 1 Assertion-Reason type question, which has 4 choices (a), (b), (c) and (d) out of which ONLY ONE is correct.
इस खण्ड में 1 कथन-कारण प्रकार का प्रश्न है, जिसमें 4 विकल्प (a), (b), (c) तथा (d) दिये गये हैं, जिनमें से केवल एक सही है।

A : Friction acts always opposite to the direction of motion of the body.
A : घर्षण सदैव पिण्ड की गति की दिशा के विपरीत कार्य करता है।

R : Force of friction increases if the two surfaces are pressed harder.
R : यदि दो पृष्ठों को जोर से दबाया जाता है, तब घर्षण बल बढ़ता है।

1. Both (A) and (R) are true and (R) is the correct explanation of (A)
   
   (A) तथा (R) दोनों सही हैं तथा (R), (A) का सही स्पष्टीकरण है

2. Both (A) and (R) are true but (R) is not the correct explanation of (A)
   
   (A) तथा (R) दोनों सही हैं लेकिन (R), (A) का सही स्पष्टीकरण नहीं है

3. (A) is true but (R) is false
   
   (A) सही है लेकिन (R) गलत है

4. (A) is false but (R) is true
   
   (A) गलत है लेकिन (R) सही है

Q. Can friction be eliminated completely? Explain.

Q.

Consider the following statements:

Statement 1: Friction is caused due to interlocking of irregularities present on the surfaces in contact.
Statement 2: Frictional force increases if the two surfaces are pressed harder.

Which of these statements is/are correct?

1. Only statement 1 is correct.

2. Only statement 2 is correct.

3. Both the statements are correct.

4. Neither of the statements is correct.

Q.

Two chairs are being dragged, one empty while other is occupied. On which chair more frictional force is exerted?

Q. The magnitude of friction does not depend on how hard the two surfaces are pressed together.

1. True
2. False

Q.

When static, sliding and rolling frictional forces are to be arranged in an increasing order, what would be the correct order? [5 MARKS]

Q. is due to presence of irregularities on a surface.

1. Softness
2. Hardness
3. Roughness
4. Smoothness

Q. Which of the following bodies will experience least drag while moving through air?

1. Ring shaped flow
2. Streamline shaped flow
3. Star shaped flow
4. Dumbell shaped flow

Q.

Which of the following is not a lubricant?

1. Oil

2. Grease

3. Graphite

4. Sand

Q. The design of formula one (F1) cars facilitates them to acquire very high speeds. The main purpose of designing these cars in special shapes is to:

1. reduce the air drag
   
2. reduce the car weight
3. provide sitting comfort to the racer
4. make them look stylish

Q. Which of the following materials cannot be used to reduce friction between the moving parts of a machine?

1. Oil
2. Grease
3. Graphite
4. Sand

Q.

What impact would decreasing irregularities on two surfaces rubbing each other have on the frictional force between them?

1. It does not have any influence

2. It increases friction

3. Cannot be determined

4. It decreases friction

Q. Smooth surface has _____ friction than a rough surface.

1. less

2. equal

3. constant

4. more

Q. why does rough surface have greater friction than smooth surface?

Q.

In which case will there be more friction between a truck and the road; when the truck is empty or when it is loaded?

Q. Which of the following bodies will experience least drag while moving through air?

1. Cubical body
2. Streamlined body
3. Spherical body
4. Cylindrical body

Q. Least amount of friction is required in which of the following sports?

1. Car race
2. Football
3. Ice skating
4. Tug of war

Q. A chain is placed on a table. Now, one-third of the length of the chain is suspended from the table. Here, find the coefficient of friction between the table and the chain.

Q. Which of the following have highly streamlined structures?

1. Aeroplanes

2. Submarines

3. Bullock carts
4. Bullet trains