CBSE Important Questions Class 6 Science Chapter 5 – Measurement of Length and Motion

Class 6 Science Chapter 5 Measurement of Length and Motion is part of the new NCERT textbook Curiosity. It teaches students how to measure length correctly using standard units such as the metre and centimetre, and how to use a scale properly. Students then learn what motion is, why we need a reference point to say that something is moving, and the different kinds of motion: linear (straight line), circular, rotational and oscillatory (to and fro).

These CBSE important questions for Class 6 Science Chapter 5 cover the meaning of motion, distance and displacement, the difference between linear and circular motion, examples of each type of motion, why a reference point is needed, whether a person in a moving bus is at rest or in motion, and the motion of a bicycle wheel compared with fan blades. Every question has a clear step-by-step answer in simple English, so students can practise on their own, parents can check the working, and teachers can use them for class tests. A free printable PDF of these important questions is also available on this page.

CBSE Important Questions Class 6 Science Chapter 5 – Measurement of Length and Motion

Q1. Define motion and provide an example from everyday life.

Answer: Motion is the change in the position of an object with time. An object is in motion when it moves from one place to another.
Example: A car moving on a road is in motion, because its position keeps changing with time as it goes from one point to another.

Q2. The numerical ratio of distance to displacement is _______________.
(a) Always equal to one
(b) Always less than one
(c) Always greater than one
(d) Equal to or more than one

Answer: (d) Equal to or more than one
Distance is the total length of the path travelled, while displacement is the shortest straight-line distance between the starting point and the ending point. The path can never be shorter than the straight line, so distance is always equal to or greater than displacement. Hence the ratio distance ÷ displacement is equal to or more than one.

Q3. Compare and contrast linear motion and circular motion.

An object moving in a straight line and an object moving along a circle

Linear motion Circular motion
The object moves along a straight line. The object moves along a circular path.
The direction of motion stays the same. The direction keeps changing as the object goes round the circle.
Examples: a car on a straight road, a person walking straight, a train on straight tracks. Examples: a merry-go-round, the blades of a fan, a satellite going round the Earth.

Answer: Both are types of motion, that is, in both the position of the object changes with time. The difference is in the path: linear motion is along a straight line, while circular motion is along a circle around a fixed point.

Q4. Which of the following is an example of linear motion?
(a) The hands of a clock
(b) A train moving on straight tracks
(c) A pendulum swinging
(d) Earth rotating around the Sun

Answer: (b) A train moving on straight tracks
Linear motion means moving in a straight line. The hands of a clock and the Earth going round the Sun show circular motion, and a swinging pendulum shows oscillatory (to and fro) motion.

Q5. In which type of motion does an object move back and forth around a fixed point?
(a) Circular motion
(b) Linear motion
(c) Oscillatory motion
(d) Uniform motion

Answer: (c) Oscillatory motion
In oscillatory motion the object moves to and fro about a fixed (mean) position, like a swing or the pendulum of a clock.

Q6. Which of the following is an example of circular motion?
(a) A car driving on a straight road
(b) A child on a swing
(c) Motion of a merry-go-round
(d) A ball bouncing up and down

Answer: (c) Motion of a merry-go-round
A merry-go-round goes round and round along a circular path about its centre, so it shows circular motion. The car shows linear motion, while the swing and the bouncing ball show oscillatory motion.

Q7. Which type of motion occurs when an object moves in a straight line?
(a) Circular motion
(b) Oscillatory motion
(c) Linear motion
(d) Rotational motion

Answer: (c) Linear motion
Motion along a straight line is called linear motion, for example a bullet fired from a gun or a car on a straight road.

Q8. Which of the following best describes motion?
(a) Staying in the same place
(b) Changing position over time
(c) Increasing in size
(d) Decreasing in size

Answer: (b) Changing position over time
An object is said to be in motion when its position changes with time. Staying in the same place is rest, and a change in size is not motion.

Q9. Why is a reference point necessary to determine if an object is in motion or not? Can motion exist without it? Explain.

Answer: Motion means a change in the position of an object with respect to some fixed point, called the reference point. To say that an object has moved, we must compare its position now with its position earlier, and we need a fixed point to make this comparison.
Without a reference point there is nothing to compare with, so we cannot tell whether the object's position has changed. That is why motion cannot be judged without a reference point.

Q10. If you are sitting in a moving bus, are you at rest or in motion? Explain in detail.

Answer: It depends on the reference point.
• With respect to the seats and the other passengers inside the bus, your position does not change, so you are at rest.
• With respect to the trees, buildings and people outside on the road, your position keeps changing as the bus moves, so you are in motion.
So the same person can be at rest for one reference point and in motion for another.

Q11. Observe the pictures given below. Write the type of motion these objects show while in action or being played.

Tabla, electric fan, pendulum, swing, potter wheel and spinning top

Answer: (a) Tabla: vibratory motion (the skin moves to and fro very fast), which is also periodic.
(b) Electric fan: circular or rotational motion.
(c) Pendulum: oscillatory motion, which is also periodic.
(d) Swing: oscillatory motion, which is also periodic.
(e) Potter's wheel: circular or rotational motion.
(f) Spinning top: circular or rotational motion.

Q12. How are the motions of the wheel of a moving bicycle and the blades of a moving electric fan different? Explain.

Answer: The wheel of a moving bicycle shows two motions at the same time. It turns round its axle (rotational motion) and it also moves forward along the road with the bicycle (linear motion).
The blades of an electric fan show only rotational motion. They turn round the centre of the fan but the fan stays in the same place, so there is no linear motion.

A bicycle wheel rotating and moving ahead, and fan blades rotating in one place

Related Study Material on Extramarks

Q.1 Identify the correct match.

      Column I Column II
i. Solute a. No more solute can be dissolved in solution at a certain temperature
ii. Solvent b. Component of solution present in lesser amount
iii. Solution c. Component of solution present in larger amount
iv. Saturated Solution d. A mixture of solid dissolved in liquid

i-c, ii-d, iii-b, iv-a

i-a, ii-b, iii-c, iv-d

i-b, ii-c, iii-d, iv-a

i-d, ii-c, iii-b, iv-a

Marks:1

Ans

i-b, ii-c, iii-d, iv-a

       Column I Column II
i. Solute b. Component of solution present in lesser amount
ii. Solvent c. Component of solution present in larger amount
iii. Solution d. A mixture of solid dissolved in liquid
iv. Saturated Solution a. No more solute can be dissolved in solution at a certain temperature b. Component of solution present in lesser amount

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