Ex.2. Answer the following questions .

1. What is a rotation of a rigid body?

2. What line is called the axis of rotation?

3. What points of a body are motionless in rotational motion?

4. What points of a body describe circular paths in rotational motion?

5. When is the angle   φ positive and when is it negative?

6. How is the angle  φmeasured?

7. What definition can we give to an angular velocity of a body?

8. When is >0 and when is <0?

 

Ex.3. Put the questions to the following answers.

1. It characterizes the time rate of change of the angular velocity of a rotating body.

2. It is equal in magnitude to the first derivative of the angular velocity.

3. The rotation is accelerated.

4. The rotation is retarded.

5. By a vector .

6. Their directions coincide.

 

Ex.4. Complete the following sentences with the information from the text.

1. In rotational motion all points of the body are motionless on………..

2. We should pass …… through the axis of rotation in order to ……...

3. The position of the body at any instant will be fully specified by……

4. The second plane passes through ….

5. Angular acceleration characterizes……

 

Ex.5. Complete the sentences with the following prepositions:

      By, between, at, along, of, through, from,  about, to, in.

1. This plane is perpendicular ……the axis of rotation.

2. Let’s pass the plane ……… the axis of rotation.

3. The position of the body …… any instant will be specified ……the angle φ …….the two planes.

4. Angle φ is always measured …….radians.

5. The angular velocity of a body can be denoted ….. a vector  of magnitude  ……. the axis of rotation of the body ….. the direction ……..which the rotation is seen as counterclockwise.

6. This vector gives the sense or rotation ……..that axis.

 

Ex.6. Match the terms and their definitions.

1	angle	a	the action of turning around a fixed point
2	fixed	b	a completely flat surface in geometry
3	instant	c	not moving at all
4	magnitude	d	the space between two straight lines or surfaces that touch or cross each other, measured in degrees
5	motionless	e	a moment
6	plane	f	a picture, symbol that has a particular meaning
7	rotation	g	firmly fastened to a particular position
8	sign	h	greatness of size or importance

Ex.7. Match: 1) the adjectives in the left column with the nouns in the right one;

                        2) the verbs in the left column with the nouns in the right one.

                        The words in the right columns can be used more than once.

	Adjectives		Nouns			Verbs		Nouns
1	angular	a	body		1	consider	a	without motion
2	average	b	point		2	describe	b	towards the value
3	circular	c	angle		3	determine	c	in radians
4	fixed	d	velocity		4	measure	d	the position
5	positive	e	path		5	remain	e	path
6	principal	f	motion		6	specify	f	the angle
7	rigid	g	acceleration		7	tend
8	rotational	h	characteristics		8	turn through