- #1

Jpyhsics

- 84

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- Homework Statement
- A hot-air balloon is initially floating (stationary) a few metres above the ground. The radius of the spherical balloon is 6.25 m, and the density of surrounding air is 1.29 kg m-3. "Ballast" is weight of negligible volume that can be dropped to make the balloon rise. How much weight would you have to drop overboard to make the balloon rise 105 m in 15.0 s? You may assume that the density of surrounding air remains constant.

- Relevant Equations
- Archimedes principle: Fb=rho*gV

Vsphere= 4/3*pi*r^3

Initially the hot air balloon is stationary so...

F

ρgV=mg

m=1319.2...kg

F

In the air...

a=2d/t^2=0.933...m/s^2

F

(1319-x)(0.93...)=12941-(1319-x)g

x=114.6 kg

but apparently this is wrong?...

F

_{B}=F_{g}ρgV=mg

m=1319.2...kg

F

_{B}=F_{g}=12941NIn the air...

a=2d/t^2=0.933...m/s^2

F

_{net}=F_{B}-F_{g}(1319-x)(0.93...)=12941-(1319-x)g

x=114.6 kg

but apparently this is wrong?...