Problem Daily @FreeProbDaily
Problems? Solved. Equipping students and teachers with free daily content for problem solving in physics and math. problemdaily.com Joined March 2020-
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How to derive Electromagnetic Waves from Maxwell's eq. in 1 Tweet 1)∇.B = 0 2)∇.E = 0 3)∇xE = -∂B/∂t 4)∇xB = μ₀ε₀∂E/∂t Using ∇x(∇xA) = ∇(∇⋅A)-∇²A for E & B ∂²E/∂t² = 1/μ₀ε₀∇²E ∂²B/∂t² = 1/μ₀ε₀∇²B E and B obey the wave eq. with c = √1/μ₀ε₀💡!
Power = work / time
The derivatives of the Position vector (x) with respect to time have interesting names Velocity (v) = change in Position Acceleration (a) = change in Velocity Jerk (j) = change in Acceleration Snap (s) = change in Jerk Crackle (c) = change in Snap Pop (p) = change in Crackle 🙂
New post: Why a little knowledge is a dangerous thing johndcook.com/blog/2020/10/0…
Our third detailed problem and solution is live! problemdaily.com/subjects/physi… What physics problems are you working on? How can we help?
SI prefix atto (a) = 10^-18.
A maxwell (Mx) is the CGS unit of magnetic flux, equal to 10^-8 weber.
All models are wrong. Some models are useful. -- George Box
Wanna learn some astronomy lingo? When the Moon is closest to Earth, that's called perigee. When it's furthest, that's called apogee. The diff between those = 27,000 miles (avg dist = 239,000 mi). The Moon is 14% larger in the sky at perigee compared with apogee and 30% brighter.
Lorentz force: F = q(E + v x B)
A newton is the amount of force needed to accelerate 1 kilogram of mass at the rate of 1 m/s^2.
A tesla is a flux density of one weber per square meter.
How to help mankind? @nntaleb has the only right answer to this question.
LASER = Light Amplification by Stimulated Emission of Radiation
On the kelvin temperature scale, absolute zero is zero. Kelvin = Celsius + 273.15.
SI prefix micro (μ) = 10^-6.
The elementary charge is now exact by definition, defining the coulomb: e = 1.602176634 × 10^-19 C.
One watt is the rate at which work is done when one ampere of current flows through an electrical potential difference of one volt.
Amplitude modulation and beats johndcook.com/blog/2016/03/1…
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