Anna was on vacation and came across an echo lake. Wanting to know how far she had to swim to get across the lake to the other side, she yelled across “Hello!”

How wide is the lake if 7 seconds later she heard her own echo? Assume that the temperature is 20 ◦C and the speed of sound is 344 m/s.
Answer in units of m.

Consider a double atwood machine constructed as follows: a mass 4m is suspended from a string that passes over a massless pulley on frictionless bearings. the other end of this string supports a second similar pulley, over which passes a second string supporting a mass of 3m at one end and m at the other. using two suitable generalized coordinates, set up the lagrangian and use the lagrange equations to find the acceleration of the mass 4m when the system is released. explain why the top pulley rotates even though it carries equal weights on each side.

You can estimate the degree to which a bond between two atoms is ionic or covalent by calculating the

It is advised not to hold the thermometer by the bulb while reading it