## Friday, July 29, 2011

### Class 7th Motion and Time Solved Questions Question:1. What is motion?

Answer: Motion is a change in the position of an object with time.

Question:2. What is rest ?

Answer: When a body do not change its position with it said to be in rest

Question:3. How can you say that motion and rest are relative ?

Answer: We have observed that the position of stars and planets change while you remain stationary. In

reality the earth is moving too. Thus, an object which appears to be at rest, may actually be in motion.
Therefore, motion and rest are relative terms.

Question:4. What is  rectilinear motion?

Answer: The motion of an object along a straight line is called rectilinear motion. For example the motion of a

vehicle on a straight road, march-past of soldiers in a parade or the falling of a stone.

Question:5. What is circular motion?

Answer: Motion of an object in a circular path is called circular motion eg. Motion of the hands of a clock.

Question:6. What is periodic motion?

Answer: When an object repeats its motion after some time. This type of motion is called periodic motion.

Eg. Motion of a pendulum , motion of a child on a swing, motion of the strings of a guitar.

Question:7. Define non-uniform motion?

If the speed of an object keeps changing in equal interval of time , while moving along a straight line, its

motion is said to be non-uniform.

Question:8. What is oscillatory motion?

Answer: The to and fro motion of an object from the position of rest is called  an oscillatory motion.

Question:9. Give an example when objects undergo combinations of different types of motion?

Answer: The motion of a ball on the ground. Here the ball is rolling on the ground and rotating as well as

moving forward on the ground. Thus, the ball undergoes a rectilinear motion as well as rotational motion.

Question:10. What is speed of an object?

Answer: The distance covered by an object in a unit time as the speed of the object. the basic unit of speed

is m/s. Of course, it could also be expressed in other units such as m/min or km/h.

Question:11. What is the difference between uniform and non uniform motion ?

Answer: Uniform motion

An object moving along a straight line with a constant speed is said to be in uniform motion.

In this case, the average speed is the same as the actual speed.

Non-uniform motion

If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform. In

this case, the average speed is different fron the actual speed.

Question:12. What is time?

The interval between two events is called time. Example: The time between one sunrise and the next was

called a day. Clocks or watches are the most common time measuring devices. The basic unit of time is a
second. Its symbol is s. Larger units of time are minutes (min) and hours (h).

Question:13. What is simple pendulum?

Answer: A simple pendulum consists of a small metallic ball or a piece of stone suspended from a rigid stand

by a thread .The metallic ball is called the bob of the pendulum.

Question:14.What is oscillation of a pendulum?

Answer: One complete to and fro motion of a pendulum from rest position is called one oscillation.

The time taken by the pendulum to complete one oscillation is called its time period. It is only depending on

the length of the string of pendulum.

Question:15. What are the different types of motion?

Answer: Translatory Motion  :  -  In translatory motion the particle moves from one point in space to

another. This motion may be along a straight line or along a curved path.

Rectilinear motion   :  Motion along a straight line is called rectilinear motion.   Example: A car moving on a

straight road

Curvilinear motion  :  Motion along a curved path is called curvilinear motion.Example: A car negotiating a

curve

Rotatory Motion :  In rotatory motion, the particles of the body describe concentric circles about the axis of

motion.

Vibratory Motion In vibratory motion the particles move to and fro about a fixed point.  Example   Simple Pendulum

Question:15. Who made the pendulum clock?

Answer: The first pendulum clock, invented by Christiaan Huygens in 1656.Huygens was inspired by investigations of pendulums by Galileo Galilei beginning around 1602.