Mechanics

Question 1

Tangential forces generated between contacting surfaces and occur to some degree in the interaction between all real surfaces

Answer 1

friction forces

Question 2

A machine or process in which friction is small enough to be neglected is said to be

Answer 2

Ideal

Question 3

When friction must be taken into account, the machine or process is termed

Answer 3

Real

Question 4

Types of friction

Answer 4

Dry
Fluid
Internal

Question 5

occurs when the unlubricated surfaces of two solids are in contact under a condition of sliding or a tendency to slide. Also called coulomb friction

Answer 5

Dry friction

Question 6

occurs when adjacent layers in a fluid (liquid or gas) are moving at different velocities.

Answer 6

Fluid friction

Question 7

occurs in all solid materials which are subjected to cyclical loading

Answer 7

Internal friction

Question 8

The region up to the point of slippage or impending motion is called

Answer 8

range of static friction

Question 9

is usually somewhat less than the maximum static friction force

Answer 9

Kinetic friction

Question 10

This opposing force, which acts in the opposite direction of the movement of the block

Answer 10

Force of friction or friction

Question 11

Two types of friction

Answer 11

Static, dynamic

Question 12

It is the friction experienced by a body when it is at rest. Or in other words, it is the friction when the body tends to move.

Answer 12

Static friction

Question 13

It is the friction experienced by a body when it is in motion. It is also called kinetic friction.

Answer 13

Dynamic friction

Question 14

Two types of dynamic friction

Answer 14

Sliding, rolling

Question 15

It is the friction, experienced by a body when it rolls over another body

Answer 15

Rolling friction

Question 16

It is the friction, experienced by a body when it slides over another body

Answer 16

Sliding friction

Question 17

is the ratio of limiting friction to the normal reaction, between the two bodies, and is generally denoted by μ.

Answer 17

coefficient of friction

Question 18

laws of static friction

Answer 18

1. The force of friction always acts in a direction, opposite to that in which the body tends to move, if the force of friction would have been absent.
2. The magnitude of the force of friction is exactly equal to the force, which tends to move the body.
3. The magnitude of the limiting friction bears a constant ratio to the normal reaction between the two surfaces.
4. The force of friction is independent of the area of contact between the two surfaces.
5. The force of friction depends upon the roughness of the surfaces.

Question 19

laws of kinetic or dynamic friction

Answer 19

1. The force of friction always acts in a direction, opposite to that in which the body is moving.
2. The magnitude of kinetic friction bears a constant ratio to the normal reaction between the two surfaces. But this ratio is slightly less than that in case of limiting friction.
3. For moderate speeds, the force of friction remains constant. But it decreases slightly with the increase of speed.

Question 20

The term that means that the cables are incapable of developing internal forces other than tension.

Answer 20

flexible

Question 21

the force of friction has a remarkable property of adjusting its ___, explain

Answer 21

magnitude, so as to become exactly equal and opposite to the applied force, which tends to produce motion.

Question 22

coefficient of friction

Answer 22

µ = F/N= tan φ
or
F=µN

φ - angle of friction
F - limiting friction
N - normal force

Question 23

P1, minimum force

Answer 23

= W × (sin (α - φ))/cos φ

Question 24

P2, maximum force

Answer 24

= W × (sin (α + φ))/cos φ

Question 25

which is used in suspension bridges, transmission lines, messenger cables for supporting heavy trolley or telephone lines, and many other applications.

Answer 25

flexible cable

Question 26

The term means that the cables are incapable of developing internal forces other than tension.

Answer 26

flexible

Question 27

Formula for Tmax ( parabolic cable)

Answer 27

T= sqrt ( To^2 + (wox)^2)

Question 28

formula for slope angle

Answer 28

tan θ = W/To

Question 29

a homogeneous cable that carries no load except its own weight

Answer 29

catenary cable

Question 30

Formula for Tmax (catenary cable)

Answer 30

T= sqrt ( To^2 + (wos)^2)

Question 31

s as a function of x & To

Answer 31

s(x) = To/wo [sinh ( wox/To)]

Question 32

Tmax as a function of x & To

Answer 32

Tmax= To [cosh(wox / To)]

Question 33

determining sag in a catenary cable

Answer 33

y=To/wo [cosh (wox/To) - 1]