Regents Problems Best Solution

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Homework Statement

Problems in pics from regents site.

Homework Equations

The Attempt at a Solution

16 and 17--
16--
U = C_v 300-275 but how do i find C_v
17 ---is zero from properties of adiabatic process.

23 How am I supposed to know its 4 without memorizing the resistance
i know R = rho L/a but I would have to memorize rho.

6 ---it has to be 3 because of maximum magnitude = 718 and 43----Same as 23 ---

I use v= at + v_o to find half of time in air above horizontal from starting point
for both balls then
used x= 0.5 g t^2 to find the rest of the time and then figured out ratio
but this way is very computationally intensive is there a better way.

30-- am I supposed to know an equation for n(lambda)

19--- same as 23

29-- the frequency stays the same but why?

 

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Does anyone know why the frequency stays the same as light passes through a medium but the wavelength and speed change?