NCERT 6th Class (CBSE) Science: Measurements and Motion

Question: How can a measured length be expressed?

Answer: Each measurement has:

1.  A number describing the numerical value.
2.  The unit in which that quantity is measured.

Question: Give one example each of the following types of motion: (a) Linear, (b) Translation, (c) Circular, (d) Periodic.

Answer: Types of motion Example

1.  Linear motion of stone falling
2.  Translatory buses
3.  Circular ceiling fan
4.  Periodic pendulum of clock

Question: Why do we need standard unit for measurement?

Answer: We need standard unit for measurement to make our judgement more reliable and accurate. For proper dealing, measurement should be same for everybody. Thus there should be uniformity in measurement. For the sake of uniformity we need a common set of units of measurement, which are called standard units. Nowadays SI units are used in science and technology almost universally.

Question: What type of motion do the following objects have?

Answer:

1. The galloping of a horse: Linear motion.
2. The needle of a sewing machine: Periodic motion.
3. Movement of a mosquito: Random motion.
4. Blade of an electric fan: Circular motion.
5. The smoke from a lighted dhoopbatti: Random motion.
6. Wheels of moving car: Linear motion and Rotational motion.

Question: Give two examples for each of the following motions:

Answer:

1. Linear motion: (a) Rolling of ball on ground, (b) Moving of bicycle on road,
2. Spinning motion: (a) Rotating fan, (b) Wheel of sewing machine.
3. Oscillatory motion: (a) Pendulum of clock, (b) Motion of a child on a swing,
4. Periodic motion: (a) Pendulum of clock, (b) Motion of a swing, heartbeat.
5. Vibrational motion: (a) String of a guitar, (b) Surface of drums.
6. Circular motion: (a) Rotation of fan, (b) Bicycle wheel.
7. Random motion: (a) Motion of football players, (b) Movement of mosquito.