Periodic motion: 1 Mark
Examples: 2 Marks
Periodic motion is that motion which is repeated at a regular time of interval.
For example: Take a stone and tie it with a string. Now, hold the string in your hand and let the stone hang from it. Pull the stone to one side with the other hand and let it go. This is a pendulum, which will go to and fro and will repeat this motion at a regular interval of time. This type of motion is known as periodic motion.  A branch of a tree moving to and fro is also an example of periodic. 

A rolling ball moves in a straight line on the ground is a combination of rectilinear and rotational motion.

Rectilinear motion: 1 Mark
Examples: 1 Mark
The motion of a body in a straight line is known as rectilinear motion. It is also known as translational motion. For example, A man/car moving on the straight road, a ball dropped from a height, a train running on the straight track will trace rectilinear path. 

The motion of an object along a straight line is termed as rectilinear motion whereas motion along a circular path is termed as circular motion. Various parts of a bicycle moving along a straight road shows different forms of motion. However, the overall motion is considered as rectilinear motion.

(i) Handlebar and seat: Handlebar and seat moves in a straight line. So they possess rectilinear motion.
(ii) Pedal: Pedal moves in a circular path, so it posses circular motion.
(iii) Wheel: Since wheels of the bicycle moves in a straight line by rotating itself, it has both circular and rectilinear motion.

Each Point: 1 Mark
1) Circular motion and periodic motion

2) Rotational motion and periodic motion

3) Periodic motion or oscillatory motion

4) Rectilinear and rotational motion

5) Rectilinear motion

Each Point: 1 Mark
1) A car moving in a straight line is an example of linear motion.

2) The motion of the blades of a fan is an example of circular motion.

3) The rotation of the earth on its axis is an example of rotational motion.

Reason: 2 Marks
Problems: 3 Marks
Since the tape is stretchable and when you will measure anything it will give inaccurate measurements. Therefore we cannot use it for measuring purposes.
Problems:
1. While measuring a distance, we need to tell someone how much tape has been stretched which is difficult to measure. It leads to incorrect measurements.
2. We cannot measure manually how much the tape has been stretched.
3. If you measure the length of an object twice using an elastic tape, then you may get different values of the same length each time. This is because elastic tapes are stretchable.

Some of the reasons for the difference in their measurement could be:
1. Different measuring devices were used.
2. The smallest length that could be measured by different devices may be different.
3. The measurement may not be along the shortest length in all the three cases.
4. The end of the corridor may not be easily accessible.
5. The measuring devices may be faulty (not standardized).

An object is in motion or at rest depending on the person who is observing it.
The objects which are moving with respect to the ground, are also moving with respect to Harshit. Hence, only another bus passing by will be moving with respect to him.

Group 1: Falling Stone is an odd one as it is moving and the other examples are at rest.
Group 2: Sleeping Camel is odd one the Camel is at rest and the other examples are in motion.