CBSE Class 6 Science Chapter 10: Motion and Measurement of Distances NCERT Solutions

Solution: Understanding different modes of transport helps us appreciate how distances are covered. Here are examples for each category:

Land Transport: These are vehicles that travel on roads or tracks. Bus Train Car Motorcycle

Water Transport: These are vessels that travel on rivers, lakes, or oceans.

Boat

Ship

Steamer

Ferry

Air Transport: These are vehicles that travel through the sky.

Aeroplane

Helicopter

Hot Air Balloon

Solution: Let's fill in the blanks with the correct terms and values related to measurement and motion:

(i) One metre is 100 cm. This is a fundamental conversion factor in the metric system.

(ii) Five kilometre is 5000 m. Since 1 kilometre equals 1000 metres, 5 kilometres is 5 times 1000 metres.

(iii) Motion of a child on a swing is periodic motion. The child moves back and forth over a regular interval of time, repeating its motion.

(iv) Motion of the needle of a sewing machine is periodic motion. The needle moves up and down in a repeating pattern as the machine operates.

(v) Motion of wheel of a bicycle is circular motion. As the bicycle moves, the wheels rotate around their central axis, tracing a circular path.

Solution: A pace or a footstep cannot be used as a standard unit of length because these measurements are not consistent. The length of a person's pace or footstep varies significantly from one individual to another. For example, an adult's footstep is longer than a child's. Even for the same person, the length of a pace can vary slightly depending on how they walk. This inconsistency makes it impossible to get a reliable and uniform measurement, which is essential for a standard unit. Standard units, like the metre, are defined precisely and are the same for everyone, everywhere, ensuring accuracy and comparability in measurements.

Solution: To arrange these lengths in increasing order, we need to understand their relative sizes. The standard metric units of length are related as follows:

• 1 kilometre (km) = 1000 metres (m)
• 1 metre (m) = 100 centimetres (cm)
• 1 centimetre (cm) = 10 millimetres (mm)

From these relationships, we can see that a millimetre is the smallest unit, followed by a centimetre, then a metre, and finally a kilometre is the largest unit among the given options. Therefore, arranging them in increasing magnitude gives:

1 millimetre, 1 centimetre, 1 metre, 1 kilometre.

Solution: We need to convert the given height from metres to centimetres and millimetres. We use the standard conversion factors:

We know that 1 metre = $100\; \backslash text\{\; cm\}$

And 1 metre = $1000\; \backslash text\{\; mm\}$

To convert 1.65 m to centimetres, we multiply by 100:

$1.65\; \backslash text\{\; m\}\; =\; 1.65\; \backslash times\; 100\; \backslash text\{\; cm\}\; =\; 165\; \backslash text\{\; cm\}$

To convert 1.65 m to millimetres, we multiply by 1000:

$1.65\; \backslash text\{\; m\}\; =\; 1.65\; \backslash times\; 1000\; \backslash text\{\; mm\}\; =\; 1650\; \backslash text\{\; mm\}$

So, the height of the person is 165 cm and 1650 mm.

Solution: We are given a distance in metres and need to convert it into kilometres. The relationship between metres and kilometres is:

$1\; \backslash text\{\; m\}\; =\; \backslash frac\{1\}\{1000\}\; \backslash text\{km\}$

To convert 3250 metres to kilometres, we divide the value in metres by 1000:

Distance in km = $\backslash frac\{3250\}\{1000\}\; \backslash text\{\; km\}$

Distance in km = $3.25\; \backslash text\{\; km\}$

Therefore, the distance between Radha's home and her school is 3.25 km.

Solution: When measuring the length of an object using a scale, we often measure the difference between the final reading and the initial reading. In this case, the initial reading is 3.0 cm and the final reading is 33.1 cm. The length of the needle is calculated by subtracting the initial reading from the final reading:

Length of the needle = Final reading - Initial reading

Length of the needle = $33.1\; \backslash text\{\; cm\}\; -\; 3.0\; \backslash text\{\; cm\}$

Length of the needle = $30.1\; \backslash text\{\; cm\}$

So, the length of the knitting needle is 30.1 cm.

Solution: Let's analyze the motion of a bicycle and a ceiling fan.

Similarity:

Both a bicycle (when moving) and a ceiling fan (when switched on) exhibit circular motion. The wheels of the bicycle rotate around their axles, and the blades of the ceiling fan rotate around the central motor, both following a circular path.

Difference:

A bicycle, when ridden on a straight road, exhibits rectilinear motion as its overall position changes in a straight line. However, a ceiling fan, while its blades move circularly, does not exhibit rectilinear motion; its position as a whole unit remains fixed, only its parts rotate.

Solution: An elastic measuring tape cannot be reliably used to measure distance because it is not a rigid measuring instrument. Elastic materials stretch when pulled.

Problems with using an elastic measuring tape:

1. Inconsistent Measurement: When you measure a distance, the amount of stretch in the elastic tape can vary depending on how tightly you pull it. If you pull it tighter, it will stretch more, giving a longer measurement than the actual distance. If you pull it loosely, it will stretch less, giving a shorter measurement. This inconsistency means you cannot get an accurate or repeatable measurement.
2. Difficulty in Communication: If you measured a distance using an elastic tape and told someone else the measurement, they would face problems. They would need to know exactly how much the tape was stretched during your measurement to get a comparable result. Without this information, their own measurement using a non-elastic tape would likely differ significantly, leading to confusion and errors. Standard, non-elastic measuring tapes are preferred because they maintain their length regardless of tension, ensuring accurate and universally understood measurements.