MOTION
Motion is a change in position of an object with respect to time.
Types of Motion
- Rectilinear Motion: Motion where objects move along a straight line. Eg: Motion of any vehicles on a straight road.
- Circulation Motion: Motion where objects move along a circular path. Eg: Rotation of earth
- Rotational Motion: A type of circular motion where an object spins on its axis, it is called rotational motion. Eg: Spinning top
- Periodic Motion: The motion of an object that repeats consistently over a unit of time. Eg: The rotation of the earth around the sun.
- Random Motion: Random motion is the type of motion that is unpredictable and the object is likely to move in any direction. Eg: Movement of gaseous molecules.
What is uniform motion?
A body is in uniform motion if it covers equal distance in equal interval of time. The speed is constant.
Eg: Taxi 1 travelling at 30 km in both first and second hour.
What is non uniform motion?
A motion in which a body covers unequal distance in an equal Interval of time. The speed is not constant. Non uniform motion is also called Accelerated motion.
Eg: Taxi 1 travelling at 40km in first hour and 50 km in second hour.
Distance
It is the length of the space between two points or between two places is called distance. The distance can never be zero or negative, it can only be positive.
Distance= Speed×Time
Displacement
Displacement measures the distance and direction from the initial to the objects to its starting point.
| Displacement= final position -initial position |
Measurement
Measurement is comparison on an unknown quantity with a known quantity. Measurement consists of two parts, a number and a unit.
Standard units of measurements
In ancient time, the length of a foot, the width of a finger, and the distance of a step were commonly used as different units of measurements. In ancient India, small length measurements used were a finger or a fist. The system of units now used is known as the international system of units. The SI unit of length is a meter.
EXAM RELATED QUESTIONS
1. Define the term standard unit?
Ans. The units that could be used everywhere as a basic unit of measurement is called a measurement.
2. Define rest and motion?
Ans. The objects which do not change their position with time are said to be at rest. The objects which change their position with time are said to be in motion.
3. What is the advantage of a distance time graph?
Ans. Distance time graph gives information about the nature of the motion of an object like uniform and non uniform motion. Motion of an object can be represented by its distance time graph.
4. Name the device on vehicles to track the distance covered?
Ans. An Odometer
5. What are the traditional ways of measuring length?
Ans. Footsteps, fingers, palms and arms is known as traditional or non standard length measurements.
6. Write the difference between Rotational motion and Periodic motion?
Ans.
| S.No. | Rotational motion | Periodic Motion |
| 01 | Movement in a circular path in relation to its axis. | Oscillatory movement along the same path again and again with same speed. |
| 02 | For ex: blades of a moving fan |
For ex: pendulum of a clock |
| wind mills | guitar strings |
- The distance between Ram’s home and his school is 4000m. Express the distance in km.
Ans.1km= 1000m
So, 4000m=4000/1000km=4km
Thus, distance between Ram’s home and his school is 4km.
- Assertion: The motion of a pendulum is periodic motion.
Reason: Pendulum repeats its motion after some time
Ans. Both assertion and reason are true and reason is the correct explanation of assertion.
- Assertion: The motion of a child on a swing is an example of periodic motion.
Reason: Periodic motion is one that repeats itself after regular interval of time.
Ans. Both A and R are true and R is the correct explanation of A
The motion of a child on a swing repeats itself after regular intervals of time; hence it is a periodic motion.
- What is the difference between distance and displacement?
Ans. Distance: The total length travelled from one point to another.
Displacement: it is the shortest distance travelled from one point to another.