Which of the following is true about producers?
a. the are to some ecosystems and not essential to any ecosystems
b. they are to all ecosystems but not essential to any ecosystems
c. they are essential to some ecosystems
d. they are essential to all ecosystems

The law of conservation of energy states that energy cannot be created or , energy can be from one substance to another. the first blank is ' destroyed ' and for the second blank is ' transferred '

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.

Acalorimeter uses the principle that thermal energy flows from hotter material to colder material until both reach the same