Which identifies a machine that converts mechanical energy into electrical energy?
a. motor
b. electromagnet
c. generator
d. turbine

The answer is the option c. generator. Generator is a machine that converts mechanical energy into electricity. The way it is made is because the mechanical movement may be transformed in rotation of magnets placed inside a coiled wire, and this induces the movement of electrons through the coiled wire. As you know electricity is the flow of electrons.

A. they hold atoms  together with a molecule.its a force that exist between molecules. hope this .

Initial velocity,  u = 4.9 m/sfinal velocity = v m/sinitial height,  h₁ =  245 m    final height, h₂ = 0a = -9.8  m/s²time taken = t secondss = ut + 0.5at²⇒  (h₂-h₁) = ut + 0.5at²⇒  0-245 = 4.9t + 0.5×(-9.8)×t²⇒ -245 = 4.9t - 4.9t²⇒ 4.9t² -4.9t -245 =0solving it, we get   t = 7.59sv  = u +  at = 4.9 -9.8×7.59 = 4.9 - 74.38 = -69.48 m/svelocity is  69.48 m/s downward