Question
Explain the differences between pure air and polluted air.
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Sonakshi investigated how a pencil cell travels on a ramp when the table is covered with different surfaces (wood, cotton cloth and silk cloth). She noted the time taken by the pencil cell to travel on each surface three times. Her results are mentioned below.
Surface | Time (s) | Time (s) | Time (s) |
Wooden | 5.01 | 4.99 | 5.21 |
Cotton cloth | 7.02 | 7.25 | 7.20 |
Silk cloth | 4.20 | 4.20 | 4.25 |
Q.1. Name the two factors on which the magnitude of a frictional force depends.
Q.2. From the chart given above, state which travelled fastest and find the average time it took.
Q.3. Explain with one example how friction can be both a positive and a negative part in our everyday life?