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DAV Class- 6 Measurement & Motion Question and Answer
Something To Know
A. Fill in the blanks.
1. The standard unit of mass is the kilogram.
2. While sitting in a moving bus, we are in motion with respect to the surroundings.
3. A moving car, going on a narrow straight road, is having a (nearly) rectilinear motion.
4. The motion, of the needle of a sewing machine, is an example of an oscillatory motion.
5. The motion of the earth, around the sun, is revolution in nature.
B. Write True or False for the following statements.
1. Measurement is needed to make correct decisions.
Answer 1: True
2. A metre scale can be used for measuring the length of a playground.
Answer 2: False
3. The motion of the moon, around the earth, is a rectilinear motion.
Answer 3: False
4. The motion, of the pedal of a bicycle, is a circular motion.
Answer 4: True
5. The motion, of a giant wheel, is a rotatory motion.
Answer 5: True
6. When we draw water from a well, we are pushing at the rope.
Answer 6: False
C. Tick the correct option.
1. The standard unit of length is the-
Answer 1: metre
2. The standard unit of time is the-
Answer 2: seconds
3. The motion, of the tip of a pen, while writing, is/an-
Answer 3: curvilinear motion
4. Which of the following four ‘ motions’ is different from the other three?
Answer 4: a fruit falling from a tree
5. The motion of a swinging pendulum is a/an-
Answer 5: oscillatory motion
D. Answer the following questions in brief.
1. How does measurement help us in our day-to-day life?
Answer 1: Measurements helps us in day to day life in the following ways-
1. When we are ill we have to take medicines in proper amount.
2. For cooking, everything must be taken of accurate measurements.
3. When we fall sick, we measure our temperature.
2. Which type of watch is used to measure time intervals in a ‘200 metre race?
Answer 2: A stopwatch is used to measure time intervals in a 200-metre race.
3. When do we consider an object to be in motion?
Answer 3: An object is in motion if it keeps on changing its position with respect to its immediate surroundings.
4. Name three different types of motions and give one example of each.
Answer 4:
(1) Oscillatory motion
Example: The swinging pendulum of a clock.
(2) Curvilinear motion
Example: Motion of the tip of a pen while writing.
(3) Periodic motion
Example: The motion of the hands of a clock.
5. State the difference between a periodic’ and a ‘non-periodic’ motion.
Answer 5:
Periodic motion- a motion is said to be periodic if it repeats itself after a regular time interval.
Non-periodic motion- a motion is said to be non-periodic if it (i) either does not repeat itself or (ii) does the repetitions in a random irregular manner.
E. Answer the following questions.
1. Why does a measurement need both a ‘number’ and a ‘unit’ for its complete specification?
Answer 1: We need both the number as well as the unit to express the measurement in a proper and complete way.
2. Why is a foot step, or a hand span, not used as a standard unit of length?
Answer 2: A foot step or a hand span cannot be used as a standard unit of length since each person’s foot step or hand span is different. As a result, a foot step or a hand span cannot be used as a conventional unit of length.
3. Radha was performing an experiment in the Science Laboratory. The metre scale, that she was using to measure the length of a string, was worn out between its 1 cm and its 2 cm marks, due to overuse.
(a) She measures the length of a string by keeping its one end at the 3.0 cm mark. If the other end of the string ‘reads’ 92.8 cm, find the length of the string.
(b) Write the precautions, to be followed, when a metre scale is being used for measuring a given length.
Answer 3(a): Initial mark = 3.0 cm
Final mark = 92.8 cm
Length of the string = Final mark – initial mark
= 92.8 – 3.0
= 89.8 cm
Answer 3(b):
Answer: Precautions to be followed are as: –
1. Keep the scale exactly along the length to be measured.
2. Zero mark of the scale should coincide with one end of the length to be measured.
3. Keep the eye vertically above the end point, and in line with the reading to be taken.
4. Don’t use worn out or broken portion of the metre scale for measuring length.
4. Explain the difference between ‘rest’ and ‘motion’. Give two examples of each.
Answer 4: Rest – An object is at rest if it does not change its position with respect to its immediate surroundings.
Example: Building and Rock.
Motion – An object is in motion if it keeps on changing its position with respect to its immediate surroundings.
Example: Moving car and Walking.
5. Distinguish between:
(a) Rectilinear and Curvilinear motion
(b) Rotation and Revolution
Give one example of each from our daily life.
Answer 5(a):
(a) Rectilinear and Curvilinear motions are distinguished by: –
Rectilinear motion — An object is considered to have rectilinear motion if the changes in its position, are all along a straight-line path.
Example: Falling of raindrop.
Curvilinear motion – When an object moves along a curved line from one position to another, it is said to have curvilinear motion.
Example: Motion of the tip of a pen while writing.
Answer 5(b):
(b) The following are the differences between rotation and revolution:
Rotation – An object is said to rotate if it continues to go ’round and round’ or spins (around a fixed ‘line’ or ‘axis) without changing its position.
Example: motion of a giant wheel.
Revolution- If an object moves around a central point, changing its location continually and usually following a (nearly) circular path, it is said to be in
revolution.
Example: The Earth revolves around the Sun.
6. Define the following types of motion:
(a) Rectilinear motion
(b) Circular motion
Give one example for each of these two types of motion.
Answer 6(a):
(a) Rectilinear motion – An object is said to have a rectilinear motion if the changes in its position, are all along a straight-line path.
Example: Falling of raindrop.
Answer 6(b):
Circular motion – When an object moves on a circular path, we then call such a motion as a Circular motion.
Example: If a ball is tied to the end of a string, and the string is whirled round and round.
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