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Chapter – 13
Motion and Time
Motion: The action or process ofmoving or beingmoved.
The distance moved by an object ina unit timeis called itsspeed.
Speed ofobjects help usto decide which one is moving faster than theother.
The speed ofan object isthe distance travelled divided by thetime taken to cover thatdistance. Its basic unit is mereper second (m/s).
Periodic events are used forthe measurement oftime. Periodic motion of a pendulum has been usedto make clocks and watches.
Motion of objects can be presented in pictorial form by their distance-time graphs. The distance-time graph for themotion of an object moving with a constant speed is a
straight line.
Types ofMotion:
(i) Uniform motion: An object moving alonga straight linewith a constant speed is said to be in uniform motion. The average speedis the sameas the actual speed.
(ii) Non-Uniform motion: If thespeed of an object moving along a straight line keeps
changing, itsmotion is saidto be non-uniform.
Speed: It is the distance covered by anobject in a unit time.Basic unit of speed = (Total distance travelled / total time taken) m/s.
Distance-Time Graph: Motion of objects canbe presented inpictorial form bytheir distance-time graphs. The distance-time graphfor the motion of an object moving with a constant speed is a straight line.
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