Class 6 - Physics - Motion and Measurement of Distance

**Question1.**

Give two examples of each of modes of transport used on land, water, and air.

Answer:

Land transport: Bus, train, motorbike.

Water transport: Boat, ship, steamer.

Air transport: Aeroplane, Helicopter.

**Question2.**

Fill in the blanks:

(i) One metre is ______________ cm.

(ii) Five kilometres is ______________ m.

(iii) Motion of a child on a swing is ______________.

(iv) Motion of the needle of a sewing machine is ______________.

(v) Motion of wheel of a bicycle is______________.

Answer:

- One metre is
__100__

__Explanation__:-

1m = 100cm.

- Five kilometres is
__5000__

__Explanation__: -

1km = 1000m. Therefore (5 x1000) = 5000m.

- Motion of a child on a swing is
__periodic__

__Explanation: - __

Periodic motion is defined as the motion which repeats itself after certain time interval. As the motion of the swing repeats itself after fixed time interval, therefore motion of the swing is a periodic motion.

- Motion of the needle of a sewing machine is
__periodic motion__.

__Explanation: - __

The needle of a sewing machine moves up and down and it repeats it with a certain time interval. Therefore it is periodic motion.

- Motion of wheel of a bicycle is
__circular motion__.

__Explanation__: -

The wheel of the bicycle attached to a fixed point. The wheel rotates around this fixed point when the bicycle moves. Therefore its motion is circular.

**Question 3**.

Why can a pace or a footstep not be used as a standard unit of length?

Answer:

A pace or a footstep cannot be used as a standard unit of length as the size of foot of two persons will be different from each other. As a result the distance measured will not be same. This will lead to confusion while measuring the lengths.

**Question 4**.

Arrange the following lengths in their increasing magnitude:-

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

Answer:

Arranging according to smaller to bigger units:-

1 millimetre < 1 centimetre < 1 metre < 1 kilometre.

1cm = 10mm.

1m = 100cm = 1000mm.

Again, 1km =1000m = 100000cm = 10000000mm.

**Question 5**.

The height of a person is 1.65 m. Express it into cm and mm.

Answer:

We know that 1 metre = 100 cm and 1 metre = 1000 mm

Height of the person = 1.65m

Therefore, 1.65 m = 1.65 × 100 = 165 cm

Hence the height of the person is 165cm.

Also, 1.65 m = 1.65 × 10 = 1650 mm.

Therefore the height of the person is 1650mm.

**Question 6**.

The distance between Radha's home and her school is 3250 m.

Answer:

We know that 1 m = (1/1000) km

So, 3250 m = (3250/1000) km = 3.25 km

**Question 7**.

While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?

Answer:

Initial reading = 3.0cm

Final reading = 33.1cm.

Therefore, the length of the needle = Final reading – Initial reading

= 33.1 cm – 3.0 cm = 30.1 cm

The length of the needle is 30.1cm.

Express this distance into km.

Answer:

We know that 1 m = (1/1000) km

So, 3250 m = (3250/1000) km = 3.25 km

**Question 8.**

Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.

Answer:

__Similarities__:-

- Both have circular motion around their fixed points.
- The blades of the fan and wheels of a bicycle are fixed at a point.

__Differences__:-

- Motion of the bicycle is linear whereas a fan does not exhibits circular motion.
- The motion of the blades of a fan is periodic, whereas the motion of a bicycle is rectilinear motion.

**Question 9.**

Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?

Answer:

An elastic measuring tape is stretchable and flexible. When the tape is stretched their length also changes. Therefore distance measured also changes. This will leads to incorrect measurements.

**Question 10.**

Give two examples of periodic motion.

Answer:

Examples of Periodic motion:-

- Motion of a pendulum: - The motion of bob of the pendulum is to and from which repeats itself after certain time interval.
- Motion of the swing.

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