Let the length of glass
tube l mm
Area of cross section of wall = Δr(2l)
Area of the cross section through axis = 2rl
Inward elastic force = Area×stress
= Δr(2l)×σ
Outward force = p×2rl
Balancing the forces we have
Δr(2l)×σ = p×2rl
p=Δr×σr
= 1×10−3×5×107/25×10−3
= 20×105 pascals
= 20 atm