Recent content by ninaw21

[b]1. The surface temperature of the sun is approximately 5800K. Given that the radius of the sun is 6.96x108m calculate the rate of energy output of the sun, taking the sun as a blackbody. [b]2. H = εσAT4 [b]3. Surface temp = 5800K, Radius of the sun = 6.96x108, Emissivity of a...

Homework Statement Calculate the magnitude of the net force on an air parcel of mass 1.0x10-3kg which is at a temperature 250K and which is in the US standard atmosphere at an altitude of 4.0km. Take the lapse rate as 6.5K/km and the surface temperature as 288K Homework Equations Force =...

I25/I15 = 2.78 10log2.78 = 4dB

do i add it to the original decibel level?

I divided I25 by I15 and got a decibel level of 3dB..Is that not very low?

Thank you! No I don't know how to calculate it can you explain it please?

Homework Statement A car horn sounds and 15 m away the sound level is recorded as 85 dB. Calculate the decibel level 25 m away from the horn. Homework Equations β = (10dB)logI/Io β = (20dB)logP/Po The Attempt at a Solution I = P/A @ 15m A = 4∏r2 A = 2827 I =...

Yes! :)

Thank you so much! :)

Is this the formula that is used then : deltaQ/deltat = kAdeltaT/d, where: deltaQ = heat flow, deltat = time, k = thermal conductivity, deltaT = temp, and d = distance ?? (Thanks for all the help!)

q = specific heat x m x Δt, where q is heat flow, m is mass in grams, and Δt is the temperature change. ??

Thank you! I know that they're equal but I don't know the variables to use..

Homework Statement Calculate the R-value of the stack of materials whose total thickness is made up of the individual thicknesses: material 1; k = 0.123 W/m/K, thickness = 0.103 m material 2: k = 0.234 W/m/K, thickness = 0.092 m material 3: k = 0.345 W/m/K, thickness = 0.081 mHence...

Thanks guys!

Homework Statement A jackhammer with a sound power of 10 W is operating in the countryside. Calculate the intensity levels at distances of 2.0 m and 50.0 m from the jackhammer. Calculate the corresponding levels in dB. Homework Equations β = (10dB) log (I/Io) where, β = sound...