An 85.0-n backpack is hung from the middle of an aluminum wire, as the drawing shows. the temperature of the wire then drops by 20.0 c. find the tension in the wire at the lower temperature. assume that the distance between the supports does not change, and ignore any thermal stress.

T = 995.95 N

Explanation:

Using the equation to find the tension in the wire

2* T * sin (φ) = m * g  

T = m∙g / (2∙sin(φ))  

cos(φ) = d/l       ⇒      d = l∙cos(φ)

we know the angle of thew "hot" wire as    φ₀ = 3°

d = l₀∙cos(φ₀)  

α = 23×10⁻⁶K⁻¹  thermal expansion coefficient of aluminum

So the length changes to

l₁ =  l₀ - ∆l = l₀∙(1 - α∙∆T)  

Since distance d does not change, the angle decreases such that:  

d = l₁∙cos(φ₁)  =   l₀ * (1 - α * ∆T) * cos(φ₁)

l₀∙cos(φ₀)   =   l₀ * (1 - α * ∆T) * cos(φ₁)

φ₁ = cos⁻¹ ( cos(φ₀)  /  (1 - α * ∆T) )  

φ₁ = cos⁻¹ ( cos(3°)  /  (1 - 23×10⁻⁶K⁻¹  * 20.0 C) )

φ₁ = 2.4457°

T = 85.0 N / (2 * sin (2.4457°) )

T = 995.95 N

wire in brush may conduct electricity from cell to drill and vice versa electrc shock possible

hi,

what occurs during a solar eclipse?

there are small tides across earth.

the moon is between earth and the sun.

p.s. im not sure if the first answer is correct because during a solar ecliphse there are spring tides and i dont know if they are the same.