Chapter 10
Measurement of Distance and Motion (Answers)
A. VERY SHORT-ANSWER QUESTIONS :
Q.1. What is the SI unit of length?
Ans. Metre (m).
Q. 2. Name two common devices used for measuring length.
Ans. Ruler, Measuring tape.
Q. 3. What is the state of an object which changes its position with time called?
Ans. State of motion.
Q. 4. What are the small and rapid oscillations called?
Ans. Vibrations.
Q. 5. Are all the passengers sitting in a compartment of a running train at rest or in motion with respect to each other ?
Ans. At rest.
B.SHORT-ANSWER QUESTIONS :
Q.1. What does each measurement consist of ?
Ans. Each measurement consists of-
a). a number describing the numerical value of the measure.
b). the unit in which the quantity is measured.
Q. 2. On what factors does the choice of measuring device depend?
Ans. The choice of a measuring device depends on the following factors.
a). the size of the object to be measured.
b). the shape of the object to be measured.
c). the degree of accuracy required.
Q. 3. What is meant by the rotatary motion ?
Ans. The motion in which a body undergoes both translatory as well as rotatory motions is called rolling motion.
Q. 4. Name the three types of translatory motion. Give one example of each type.
Ans. Translatory motion is of three types :
(a)Linear Motion (or Rectilinear Motion).
(b)Curvilinear Motion
(c)Random Motion
The motion of a car along a straight line or motion of a stone dropped from a height is an example of linear motion.
The motion of a car along a curved path is an example curvilinear motion.
The motion of an ant or a fly is an example of random motion.
Q. 5. Define random motion. Give one example.
Ans. The translatory motion of a body which keeps on changing its direction in a disorderly manner is called random motion. For example, the motion of a football or hockey player on the ground is an example of random motion.
C. LONG-ANSWER TYPE QUESTIONS :
Q.1. Why do we need standard units for measurements?
Ans. Need of standard units: A standard unit of measurement is needed for the sake of uniformity. The unit that can be used everywhere uniformly as a basic unit of measurement is called a standard unit. For example, the standard unit of length is metre and that of time is second.
Q. 2. Mention the precautions to be observed while measuring the length of a pencil using a ruler.
Ans. Precautions :
(i) The scale should be placed along the length to be measured. The scale should be placed very close to the object to be measured.
(ii) Keep your eye in line with the point of measurement. If the eye is not in line with the point of measurement, the measured length will be either shorter or longer than the actual length.
(iii) Do not start the measurement from the worn-out or damaged end of the scale. If the zero end of the scale is damaged, start the measurement from some other mark of the scale. Then the actual length of the object is equal to the difference between the readings at the two points.
Q. 3. While measuring the length of a metallic rod the reading of the scale at one end is 8.0 cm and at the other end is 33.7 cm. What is the length of the rod ?
Ans. Reading of scale at one end = 8.0 cm.
Reading of scale at other end = 33.7 cm.
Length of the metallic rod = 33.7 cm – 8.0 cm = 25.7 cm
The length of the metallic rod is 25.7 cm.
Q. 4. Name the types of motion executed by a rolling body. Give one example of rolling motion.
Ans. A rolling body executes both translatory as well as rotatory motion. The motion of a bicycle wheel or the motion of a cylinder on an inclined plane are examples of rolling motion.
Q. 5. Define circular motion. Give one example also.
Ans. The motion of a body along a circular path is called circular motion.
Example: The whirling of a stone tied to a string is an example of circular motion.
D. TICK (4) THE ODD-ONE OUT GIVING REASON
1.Aeroplane, Bus, Railway train, Ship, Bullock cart
2.Metre, Kilometre, Yard, Centimetre
3.Handspan, Palm, Foot, Cubit
4.Motion of a stone dropped from certain height, Motion of a fly, Motion of a bullet fired from a gun (up to short distance), Motion of a car on a straight road
5.Motion of the moon around the earth, Motion of the earth around the sun, Motion of a merry-go-round, Heart-beat in a healthy person
Ans.
1. Bullock cart: Others are faster modes of transport.
2. Yard: Others are bigger or smaller units in terms of metre.
3. Foot: Others are measurements by hand.
4. Motion of a fly: Others are examples of rectilinear motion.
5. Motion of a merry-go-round: Others are examples of periodic motion.
E. DEFINE THE FOLLOWING TERMS
1.The position of rest.
Ans. The objects which do not change their positions with time with respect to their surroundings are said to be at rest.
2.Curvilinear motion.
Ans. The movement of a body along a curved path is called curvilinear motion.
3.Standard unit of measurement.
Ans. The unit that could be used everywhere as a basic unit of measurement is called a standard unit of measurement.
4.Periodic motion.
Ans. The motion which repeats itself at a regular interval of time is called periodic motion.
5.Vibratory motion.
Ans. Small and rapid to-and-fro movement of a body or a part of it from its mean position is called vibratory motion.
HIGHER ORDER THINKING SKILLS :
Q.1. A body moves as a whole. All parts of the body move through the same distance. What type of motion is this ?
Ans. This is translatory motion.
Q. 2. A turning screw undergoes two kinds of motion at the same time. Identify the two kinds of motion.
Ans. Turning screw undergoes a circular motion and a linear motion in forward direction along with it.
Q. 3. A student has to measure the length of his pencil. The zero mark on the scale is not clearly visible. How should he use the scale to get the correct length of the pencil ?
Ans. The student can measure the length from the 1cm mark on the scale and add 1cm later to his measurement. This will give him the correct length of the pencil.
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ReplyDeleteSir we don't have to do the HOTS ?
ReplyDeleteYes. we have to do HOTS.
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