CBSE Class 6 General Science Practice Worksheets | PDF - Free Printable

Here are the answers to your assignment questions.

Q1. What is a unit? Why do we need standard units?
A unit is a fixed quantity used as a standard for measurement. For example, when we say a table is "2 meters" long, "meter" is the unit.
We need standard units so that measurements are the same for everyone. If everyone used their own hand span or footstep to measure, the results would be different because people have different sizes. Standard units ensure accuracy and allow people to communicate measurements clearly.

Q2. What is the standard unit of length?
The standard unit of length in the International System of Units (SI) is the meter (m).

Q3. Name the various units of measurement used in ancient times.
In ancient times, people used body parts or everyday objects to measure. Common units included:
* Hand span
* Cubit (length from elbow to fingertip)
* Footstep
* Yard
* Angul (finger width)

Q4. Why are hand span and cubit not used as standard units?
Hand spans and cubits are not used as standard units because they vary from person to person. One person’s hand span might be 15 cm, while another’s might be 18 cm. This leads to confusion and incorrect measurements. A standard unit must be the same everywhere.

Q5. Convert:
*(Note: 1 cm = 10 mm, 1 km = 1000 m, 1 m = 100 cm)*

1. 142 cm = \_\_\_\_\_\_ mm
* Calculation: $142 \times 10 = 1420$
* Answer: 1420 mm

2. 5.4 km = \_\_\_\_\_\_ m
* Calculation: $5.4 \times 1000 = 5400$
* Answer: 5400 m

3. 7.5 m = \_\_\_\_\_\_ cm
* Calculation: $7.5 \times 100 = 750$
* Answer: 750 cm

Q6. Name the suitable measuring device you would choose to measure:

1. The size of your chest: Measuring tape (flexible tape)
2. The length of a piece of cloth: Meter scale or Measuring tape
3. The length of a line segment: Ruler (or scale)
4. The girth of a tree: Measuring tape

Q7. Mention the various precautions that you must keep in mind while taking measurements of the length of an object.
1. Place the scale in contact with the object along its length.
2. Make sure the zero mark of the scale coincides with one end of the object. (If the zero mark is worn out, start from the next full mark, like 1 cm, and subtract it later).
3. Keep your eye directly above the point where you are reading the measurement to avoid parallax error (reading from an angle).

Q8. While measuring the length of a match box, the reading at one end is 1.0 cm and at the other end is 4.3 cm. What is the actual length of the match box?
To find the length, subtract the starting reading from the ending reading.
* Ending reading: 4.3 cm
* Starting reading: 1.0 cm
* Length = $4.3 - 1.0 = 3.3$ cm

Actual length: 3.3 cm

Q9. Describe how you would measure the length of a curved line using a thread.
1. Take a flexible thread and place one end of it at the starting point of the curved line.
2. Carefully lay the thread along the curve until you reach the end point. Mark the thread at this end point.
3. Straighten the thread and place it against a ruler (scale).
4. Measure the distance between the starting end and the marked point on the thread using the ruler. This gives you the length of the curved line.

──────────────────────────────────────

Final Answer:
Q1: A unit is a fixed standard quantity. We need standard units to ensure measurements are consistent and accurate for everyone.
Q2: Meter (m).
Q3: Hand span, cubit, footstep, yard, angul.
Q4: Because they vary from person to person and are not fixed.
Q5:
1. 1420 mm
2. 5400 m
3. 750 cm
Q6:
1. Measuring tape
2. Meter scale / Measuring tape
3. Ruler
4. Measuring tape
Q7: Align scale with object, align zero mark correctly, and keep eye vertically above the reading point.
Q8: 3.3 cm
Q9: Lay a thread along the curve, mark the ends, straighten the thread, and measure it against a ruler.