Physics

Important points

1. 1

   SI units: force — newton, work — joule, power — watt, electric current — ampere.

2. 2

   Newton's first law of motion is also called the law of inertia.

3. 3

   The speed of light in vacuum is about 3 × 10⁸ m/s.

4. 4

   Sound cannot travel through a vacuum and travels fastest in solids.

5. 5

   The audible range of the human ear is 20 Hz to 20,000 Hz.

6. 6

   Acceleration due to gravity on Earth is about 9.8 m/s².

7. 7

   A rainbow forms through refraction, dispersion and total internal reflection of light in water droplets.

8. 8

   The sky looks blue because of the scattering of light.

9. 9

   Myopia is corrected with a concave lens and hypermetropia with a convex lens.

10. 10

    An electric fuse works on the heating effect of current.

11. 11

    Ohm's law: V = IR.

12. 12

    Absolute zero is 0 K, which equals −273.15 °C.

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