### Motion and Time - Revision Notes

CBSE Class 7 Science

Revision Notes
Chapter – 13
Motion and Time

• Motion: The action or process of moving or being moved.
• The distance moved by an object in a unit time is called its speed.
• Speed of objects help us to decide which one is moving faster than the other.
• The speed of an object is the distance travelled divided by the time taken to cover that distance. Its basic unit is mere per second (m/s).
• Periodic events are used for the measurement of time. Periodic motion of a pendulum has been used to make clocks and watches.
• Motion of objects can be presented in pictorial form by their distance-time graphs.
• The distance-time graph for the motion of an object moving with a constant speed is a straight line.

• Types of Motion:
(i) Uniform motion: An object moving along a straight line with a constant speed is said to be in uniform motion. The average speed is the same as the actual speed.
(ii)  Non-Uniform motion: If the speed of an object moving along a straight line keeps changing, its motion is said to be non-uniform.

• Speed: It is the distance covered by an object in a unit time. Basic unit of speed is m/s.

• Distance-Time Graph: Motion of objects can be presented in pictorial form by their distance-time graphs. The distance-time graph for the motion of an object moving with a constant speed is a straight line.