B.
Give reasons for the following statements.
1. The motion of the earth is an example of multiple motion.
2. Rest and motion are relative terms.
3. Rotatory motion is different from translatory motion.
4. The weight of an object is not a constant quantity.
5. Dancing is an example of a non-periodic motion.
Answers
1. When a body possesses more than one simple motion, it is called a multiple motion. Here, Earth is moving around the Sun (Periodic Motion) and Earth rotating on it's orbit (Rotating Motion ).
2.Rest and motion are the relative terms because they depend on the observer's frame of reference. So if two different observers are not at rest with respect to each other, then they too get different results when they observe the motion or rest of a body.
3.Translational motion is a motion in which the relative velocities between any two particles of the body is zero.
Non-Translational or Rotational motion is a motion in which the relative velocities between any two particles of the body is non-zero.
4.Consider an object with mass 1kg whose weight would be 9.81 N approx. on earth. It would be less in Mars due to variation in gravity. Weight of an object varies from place to place due to variation in gravity at different places. There are factors due to which acceleration due to gravity may vary . Like altitude, latitudes and even the spinning of our planet may vary acceleration due to gravity at different places on earth. Sometimes even geological factors account to change in value of acceleration due to gravity.
5. Periodic motion is defined as a type of motion in which a particular motion is repeated in equal intervals of time. Non-Periodic motion on the other hand includes motion which can take place at any time. A dancer performs moves which don't always take place in equal intervals of time.
So, dancing is considered to be an example of Non-Periodic motion.