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INDIABIX > mechanics > Flashcards

mechanics Flashcards

1
Q

Engineer’s units of force, is

[A]. Newton in absolute units @
[B]. Dyne in absolute units
[C]. Newton and dyne in absolute units
[D]. All the above.

A

Newton - SI unit.

Dyne - CGS unit.

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2
Q

One Newton force, is

[A].	10^3 dynes
[B].	10^4 dynes
[C].	10^5 dynes	@
[D].	10^6 dynes
[E].	10^7 dynes.
A

One Newton force, is

[A].	10^3 dynes
[B].	10^4 dynes
[C].	10^5 dynes	@
[D].	10^6 dynes
[E].	10^7 dynes.
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3
Q

The angle which an inclined surface makes with the horiontal when a body placed on it is on the point of moving down, is called

[A]. angle of repose @
[B]. angle of friction
[C]. angle of inclination
[D]. none of these.

A

The angle which an inclined surface makes with the horiontal when a body placed on it is on the point of moving down, is called

[A]. angle of repose @
[B]. angle of friction
[C]. angle of inclination
[D]. none of these.

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4
Q

A satellite moves in its orbit around the earth due to

[A]. Gravitational force
[B]. Centripetal force @
[C]. Centrifugal force
[D]. none of these.

A

may be wrong actually

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5
Q

If three rigid rods are hinged together to form a triangle and are given rotary as well as translatory motion, the number of instantaneous centres of the triangle, will be

[A].	1
[B].	2
[C].	3	@
[D].	4
[E].	5.
A

If three rigid rods are hinged together to form a triangle and are given rotary as well as translatory motion, the number of instantaneous centres of the triangle, will be

[A].	1
[B].	2
[C].	3	@
[D].	4
[E].	5.
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6
Q

To attain the synchronous orbit, the launch of a satellite, is done from a place

[A].	on equator	@
[B].	on 30° latitude
[C].	on 45° latitude
[D].	on 60° latitude
[E].	on the poles.
A

To attain the synchronous orbit, the launch of a satellite, is done from a place

[A].	on equator	@
[B].	on 30° latitude
[C].	on 45° latitude
[D].	on 60° latitude
[E].	on the poles.
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7
Q

The length of a Second’s pendulum, is

[A].	99.0 cm
[B].	99.4 cm	@
[C].	100 cm
[D].	101 cm
[E].	101.10 cm.
A

T = 2ω * L/G.

Put T= 2 Sec, G= 9.81 you get L = 0.994.

A seconds pendulum is a pendulum whose period is precisely two seconds; one second for a swing in one direction and one second for the return swing.

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8
Q

The C.G. of a right circular cone lies on its axis of symmetry at a height of

[A].	h/2
[B].	h/3
[C].	h/4	@
[D].	h/5
[E].	h/6.
A

The C.G. of a right circular cone lies on its axis of symmetry at a height of

[A].	h/2
[B].	h/3
[C].	h/4	@
[D].	h/5
[E].	h/6.
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9
Q

The centre of gravity of a triangle is at the point where three

[A]. medians of the triangle meet @
[B]. perpendicular bisectors of the sides of the triangle meet
[C]. bisectors of the angle of the triangle meet
[D]. none of these.

A

The centre of gravity of a triangle is at the point where three

[A]. medians of the triangle meet @
[B]. perpendicular bisectors of the sides of the triangle meet
[C]. bisectors of the angle of the triangle meet
[D]. none of these.

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10
Q

The locus of the instantaneous centre of a moving rigid body, is

[A]. straight line
[B]. involute
[C]. centroid @
[D]. spiral.

A

The locus of the instantaneous centre of a moving rigid body, is

[A]. straight line
[B]. involute
[C]. centroid @
[D]. spiral.

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11
Q

A projectile is thrown at an angle a to the horizontal with α velocity v. It will have the maximum centripetal acceleration

[A]. at the start @
[B]. at the top of the trajectory
[C]. as it strikes the ground
[D]. else where.

A

Projectile: Pv and Ph forces act simultaneously.

Any vehicle wheel has max acceleration at it starts only…
Therefore, it has max acceleration at the start only.

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12
Q

The resolved part of the resultant of two forces inclined at an angle θ in a given direction is

[A]. algebraic sum of the resolved parts of the forces in the direction @
[B]. arithmetical sum of the resolved parts of the forces in the direction
[C]. difference of the forces multiplied by cosine θ°
[D]. sum of the forces multiplied by the sine θ
[E]. sum of the forces multiplied by the tangent θ°.

A

The resolved part of the resultant of two forces inclined at an angle θ in a given direction is

[A]. algebraic sum of the resolved parts of the forces in the direction @
[B]. arithmetical sum of the resolved parts of the forces in the direction
[C]. difference of the forces multiplied by cosine θ°
[D]. sum of the forces multiplied by the sine θ
[E]. sum of the forces multiplied by the tangent θ°.

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13
Q

The velocity ratio of the differential wheel and axle is

[A].
[B]. @
[C].
[D].

A

Actual formula = 2R/(r1 - r2).

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14
Q

Lami’s theroem states that

[A]. three forces acting at a point are always in equilibrium
[B]. if three forces acting on a point can be represented in magnitude and direction by the sides of a triangle, the point will be in the state of equilibrium
[C]. three coplaner forces acting at a point will be in equilibrium, if each force is proportional to the sine of the angle between the other two @
[D]. three coplaner forces acting at a point will be in equilibrium if each force is inversely proportional to the sine of the angle between the other two
[E]. none of these.

A

The correct option is D.

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15
Q

To avoid bending action at the base of a pier,

[A]. suspension and anchor cables are kept at the same level
[B]. suspension and anchor cables are fixed to pier top @
[C]. suspension cable and anchor cables are attached to a saddle mounted on rollers on top of the pier
[D]. none the these.

A

To avoid bending action at the base of a pier,

[A]. suspension and anchor cables are kept at the same level
[B]. suspension and anchor cables are fixed to pier top @
[C]. suspension cable and anchor cables are attached to a saddle mounted on rollers on top of the pier
[D]. none the these.

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16
Q

If the horizontal range is 2.5 times the greatest height, the angle of projection of the projectile, is

[A]. 57°
[B]. 58° @
[C]. 59°
[D]. 60°.

A

Horizontal range,R= (u^2sin(2$))/g……..(eq1)
Maximum height,H=(u^2sin^2($))/2g……..(eq2)

Here,
Horizontal range= 2.5Maximum height
R=2.5H…..(eq3)

Substitute eq 1 & eq 2 in eq3

Sin(2$)=(2.5sin^2($))/2
2sin($)cos($)= (2.5sin^2($))/2
tan($)=1.6
$=57.99°=58°

17
Q

The shape of a suspended cable under its own weight, is

[A]. parabolic
[B]. circular
[C]. catenary @
[D]. elliptical.

A

The shape of a suspended cable under its own weight, is

[A]. parabolic
[B]. circular
[C]. catenary @
[D]. elliptical.

18
Q

A Seconds pendulum executes

[A].	0.5 beat per second
[B].	1.0 beat per second
[C].	2.0 beats per second	@
[D].	2.5 beats per second
[E].	3 beats per second.
A

Here,

1 beat per second
1 oscillation per 2 second
0.5 frequency of oscillation

T=2π √ L/g,
Where L=1,
g = 9.81.

19
Q

A ball moving with a velocity of 5 m/sec impinges a fixed plane at an angle of 45° and its direction after impact is equally inclined to the line of impact. If the coefficient of restitution is 0.5, the velocity of the ball after impact will be

[A].	0.5 m/sec
[B].	1.5 m/sec
[C].	2.5 m/sec	@
[D].	3.5 m/sec
[E].	4.5 m/sec.
A

didnt understand

20
Q

The following factor affects the orbit of a satellite up to an altitude of 720 km from the earth’s surface

[A]. uneven distribution of the gravitational field
[B]. gravity of the sun and the moon
[C]. aerodynamic forces
[D]. none of these. @

A

The gravitational field is even over the earth atmosphere and also earth’s gravitational pull plays a major role rather than that of sun and moon.

It all depend on upon the escape velocity and the velocity at which satellite is placed into the orbit.

21
Q

Newton’s law of Collision of elastic bodies states that when two moving bodies collide each other, their velocity of separation

[A]. is directly proportional to their velocity of approach
[B]. is inversely proportional to their velocity of approach
[C]. bears a constant ratio to their velocity of approach @
[D]. is equal to the sum of their velocities of approach.

A

Coefficient of restitution “e”=
[relative velocity of separation/relative velocity of approach]
For perfectly elastic there is no lose in bombardment.=> e=1,;;;;;
Where e is b/w 0

22
Q

The angle of friction is :

[A]. The ratio of the friction and the normal reaction
[B]. The force of friction when the body is in motion
[C]. The angle between the normal reaction and the resultant of normal raction and limiting friction @
[D]. The force of friction at which the body is just about to move.

A

The angle of friction is :

[A]. The ratio of the friction and the normal reaction
[B]. The force of friction when the body is in motion
[C]. The angle between the normal reaction and the resultant of normal raction and limiting friction @
[D]. The force of friction at which the body is just about to move.

23
Q

The c.g. of the shaded area of the below figure from the x-axis is
y=x^2
xmax=A , ymax =B

A

from x axis = 0.3 B

from y axis = 0.25 A

24
Q

For the given values of initial velocity of projection and angle of inclination of the plane, the maximum range for a projectile projected upwards will be obtained, if the angle of projection is

[A].	α =  - 
[B].	α =  + 	@
[C].	α =  - 
[D].	α =  - 
[E].	α =  -
A

It’s π/4 + β/2.

couldnt understand

25
Q

P is the force acting on a body whose mass is m and acceleration is f. The equation P - mf = 0, is known as

[A]. equation of dynamics @
[B]. equation of dynamic equilibrium
[C]. equation of statics
[D]. none of these.

A

It is also called as D-Alembert, s Principal.

26
Q

Principle of Transmissibility of Forces states that, when a force acts upon a body, its effect is

[A]. maximum if it acts at the centre of gravity of the body
[B]. different at different points on its line of
[C]. same at every point on its line of action @
[D]. minimum if it acts at the C.G. of the body
[E]. none of these.

A

Principle of Transmissibility of Forces states that, when a force acts upon a body, its effect is

[A]. maximum if it acts at the centre of gravity of the body
[B]. different at different points on its line of
[C]. same at every point on its line of action @
[D]. minimum if it acts at the C.G. of the body
[E]. none of these.

27
Q

A number of forces acting simultaneously on a particle of a body

[A]. may not be replaced by a single force
[B]. may be replaced by a single force @
[C]. may be replaced by a single force through C.G. of the body
[D]. may be replaced by a couple
[E]. none of these.

A

A number of forces acting simultaneously on a particle of a body

[A]. may not be replaced by a single force
[B]. may be replaced by a single force @
[C]. may be replaced by a single force through C.G. of the body
[D]. may be replaced by a couple
[E]. none of these.

28
Q

The force acting on a point on the surface of a rigid body may be considered to act

[A]. at the centre of gravity of the body
[B]. on the periphery of the body
[C]. on any point on the line of action of the force @
[D]. at any point on the surface normal to the line of action of the force.

A

The force acting on a point on the surface of a rigid body may be considered to act

[A]. at the centre of gravity of the body
[B]. on the periphery of the body
[C]. on any point on the line of action of the force @
[D]. at any point on the surface normal to the line of action of the force.

29
Q

A satellite is said to move in a synchronous orbit if it moves at an altitude of 36, 000 km with a maximum velocity of about

[A].	7000 km per hour
[B].	8000 km per hour
[C].	9000 km per hour
[D].	10, 000 per hour
[E].	11, 000 km per hour.	@
A

A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth’s rotation period (24 hours). Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky so T=24 hours.

Distance covered by any satellite = (radius of the earth+traveling distance by satellite)*2*3.14.
=(6,371 km+36000)x2x3.14.
=266089.88 km.
Velocity= distance/time.
= 266089/24.
= 11,087 km/hr.

Says 11000 km/hr.

30
Q

The instantaneous centre of a member lies at the point of intersection of two lines drawn at the ends of the member such that the lines are inclined to the direction of motion of the ends at

[A]. 30°
[B]. 45°
[C]. 60°
[D]. 90° @

A

The instantaneous centre of a member lies at the point of intersection of two lines drawn at the ends of the member such that the lines are inclined to the direction of motion of the ends at

[A]. 30°
[B]. 45°
[C]. 60°
[D]. 90° @

INDIABIX (17 decks)

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