[ Concept ] Why does angle have unit? | Small angle approximations | Solid angle | NEET & JEE

In this video I address some pressing questions like
Why is a full circle 360 degrees? 05:11
Why does angle have unit? 09:11
Can other non-dimensional quantities also have unit? 12:00
Is the angle in degree or radian? 20:46

Contents:
Intro 00:00
1. What is angle? 01:54
2. How to measure? Degree vs Radian 03:22
a. Why is a full circle 360 Degrees? 03:11
b. Degrees: Decimal vs Minute/Second 06:58
3. No dimensions, but has unit. Why? 09:11
a. What does dimensionless mean? 10:37
b. Aspect-ratio is also dimensionless. Can it have unit? 12:00
4. What is Pi (π)? Is π = 180 degrees? 14:23
5. Why θ = l/r, and not h/r, etc. ? 16:32
Trigonometric functions; Angle vs Slope 18:32
Small angle approximations; Is θ in deg or rad? 19:36 20:46
6. Angle between lines and planes 23:44
7. Plane angle vs. Solid angle 25:19
8. Applications in Physics 28:24

Problems:
28:38 1. In the definition of an angle ...
29:01 2. Mark all the correct statements ...
30:24 3. For small angles, sin⁡θ=θ. So, sin⁡0.1°≈0.1. True or False
30:39 4. sin9°≈ ____
31:29 5. For small angles, angle (in radians) and the slope are the same. True or False
31:47 6. The restoring force on a simple pendulum is ...
33:25 7. For small angles, sin⁡θ is linear in θ (sin⁡θ=θ). Similarly, cos⁡θ is ...
37:43 8. If cos⁡θ=0.9, θ is approximately
38:30. 9. Wave equation is given as ...
40:24 10. What is the solid angle subtended at one corner of a cuboid
40:50 11. Solid angle of a cone ...
45:16 Remarks ...

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