Periodic Motion

Periodic Motion or Oscillatory Motion: When an object repeats its motion after every fixed interval of time, the motion of the object is called PERIODIC MOTION OR OSCILLATORY MOTION.

simple pendulum

In many wall clocks pendulum is used even today. A device having a string suspended with a fixed point with a bob at bottom is called pendulum.

The motion of pendulum starting from one extreme end to another extreme end and back to the first extreme end is called one oscillation. Similarly, the motion of a simple pendulum from its mean position to extreme left and extreme right and back to the mean position is called one oscillation.

Time Period: Time taken to complete one oscillation by the pendulum is called time period.

Time Period = time/number of oscillations

Review Question:

Question 1: A pendulum takes 20 second to complete 10 oscillations, calculate its time period.

Answer: Given, Number of oscillations = 10

Time taken = 20 second

We know that, Time Period = Time ÷ number of oscillations

= 20 ÷ 10 = 2 second

Speed and Time

Unit of Time: Time is measured in second. Thus, unit of time is second. Second is denoted by ā€˜sā€™.

60 second = 1 minute

60 minute = 1 hour

24 hour = 1 day

7 day = 1 week

365 days = 1 year

Unit of speed: Unit of speed is meter/second (m/s), or metre/minute (m/min) or kilometer/hour (km/h).

1000 metre (m) = 1 kilometer (km)

Speedometer: A device used to measure the speed of a vehicle is called SPEEDOMETER.

Odometer: A device used to measure the distance covered by a vehicle.

Distance Time Graph: When distance covered by an object and time taken to cover the distance is represented on a graph, the graph is called distance time graph.

If a vehicle cover a distance of 5 km every hour and travels for 5 hours, the time distance time graph for the given vehicle can be plotted as follows using the table given below:

Time(in hour)12345
Distance(in km)510152025
distance time graph

Distance time graph of a moving vehicle with a constant speed is a straight slanting line.

Speed-time graph for the same vehicle will be a straight line parallel to x-axis.

speed time graph

Important Points:

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