Chapter 5

Question 1

Angular Displacement

Answer 1

The angle subtended by the center of a circle by a body moving along the circumference in a given time.
The SI unit of angular displacement is Radian.
it has no dimension.

Question 2

Angular Velocity

Answer 2

The time rate of change of angular displacement.
Unit:
The SI unit of angular velocity is rad/sec.

Direction:
its direction is along the axis of rotation and can be determine by right hand rule.
It is a vector quantity.

Question 3

Angular Acceleration

Answer 3

The time rate of change of angular velocity.
Direction:
It is vector quantity.
The direction of angular acceleration is along the axis of rotation.

Unit:
The SI unit of angular acceleration is rad/sec²

Question 4

Average Angular Acceleration.

Answer 4

The ratio of the total change in angular velocity to the total time interval.

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Question 5

Instantaneous angular acceleration.

Answer 5

The limiting value of Δω over Δt as the time interval Δt approaches to zero.
so, ains = lim Δω over Δt and lim Δω over Δt arrow 0

Question 6

Centripetal Force

Answer 6

The force which bends the normally straight path of a particle into circular path.

Examples:
1: Force acting on earth around the sun.
2: Force acting on artifical and natural satellites.

Direction:
The direction of centripetal force is in the direction of centripetal acceleration.

Unit of centripetal force is Newton and Dimensions are [MLT-2]

Question 7

Centripetal Acceleration

Answer 7

The instantaneous acceleration of an object travelling with uniform speed in a circle is directed towards the center of the circle.

Question 8

Moment of Inertia

Answer 8

Is defined as “ the product of mass of particle and square of its perpendicular distance from the axis of rotation”
It is denoted by I and is given by
I=mrsquare2
Unit:
unit is kgm2 and dimension is [ML2]

Question 9

Angular Momentum

Answer 9

The product of moment of inertia and angular velocity of a rotating body.

Direction:
the direction of angular momentum is perpendicular to the plane of rotation. It can be determined by right hand rule.

Unit: SI unit of angular momentum is kgm2/s or Js and dimension are [MLSQUARE2 T-1]

Question 10

Spin Angular Momentum

Answer 10

Angular momentum of a spinning body. it is denoted by (Ls)

Question 11

Oribtal Angular Momentum

Answer 11

Angular momentum of a body orbiting in a circular path. (Lo)

Question 12

Point Object

Answer 12

When the orbital radius is larger as compared to the size of the body, the body may be considered as a point object.

Question 13

Law of Conservation of Momentum

Answer 13

If no external torque acts on a system then the total angular momentum of the system remains constant.

Question 14

Rotiational kinetic energy and its uses

Answer 14

The energy possesed by the body due to its rotation about an axis is called.

Uses:
Rotational kinetic energy is used by flywheels, which are essential parts of many engines. A flywheel stores energy between the power strokes of the pistons, ensuring that energy is uniformly distributed over the full revolution of the crankshaft, thus maintaining smooth rotation.

Question 15

what are atrifical satellites

Answer 15

Artificial satellites are man-made objects placed into orbit around the Earth or other celestial bodies. They are used for various purposes such as communication, navigation, weather monitoring, scientific research, and surveillance. They are kept into their orbit by gravitational attraction of earth.

Question 16

Critical Orbital Velocity

Answer 16

The minimum velocity required to put a satellite into an orbit close to the earth is called

Question 17

What is real and apparent weight. Find the apparent weight in different cases for any object suspended by a string balance in an elevator.

Answer 17

Real weight:
It is the gravitational pull of the earth on the object.

Apparent Weight:
The readng of the spring balance when the object is accelerating up or down is called

Question 18

Gravity free system

Answer 18

No force is required to hold an object falling in the frame of reference of the space satellites. Such a system is called gravity free system.

Question 19

Orbital Velocity

Answer 19

The velocity of satellite with which it revolves around the earth is called.

Question 20

Orbital Motion

Answer 20

The earth and some other planet revolve around the sun in nearly circular orbits. This type of motion is called orbital motion.

Question 21

What is artificial gravity? Derive expression for frequency of spaceship required to provided the artificial gravity?

Answer 21

Artificial gravity is the gravity like effect produced in an orbiting satellite by spinning it around its own axis.

Question 22

What are geo-stationery orbits and geo-stationery satellites? Find the orbital radius of geo-stationary satellites?

Answer 22

Geostationary orbits:
The orbit in which the period of rotation of satellite is exactly equal to the period of rotation of earth about its axis, is called

Geostationary satellites:
The satellite which completes its one revolution around earth in 24 hours is called.

Question 23

Write a short note on communication satellites? also its uses

Answer 23

A communication satellites can be set up by placing several geo-stationery satellites in orbit over different point on the surface of earth. Such a satellite covers 120 of longitutude. So the whole of the populated earth’s surface can be covered by three correctly positioned satellites.

Use of wave for communication:
Microwaves are used in communicatioal network because they travel in a narrow beam, in straight line and can pass easily through atmosphere of the earth.

Question 24

What are Newton’s and Einstein views about gravitation?

Answer 24

ccording to Newton’s theory, gravitation is the intrinsic property of matter that every particle of matter attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Einstein theory about gravitation.

According to Einstein’s theory, gravity is due to the curvature of space and time caused by masses.