Suppose that during any period of ¼ second there is one instant at which the crests or troughs of component waves are exactly in phase and maximum reinforcement occurs. how many beats will occur in 1 second?

a. 8
b. 4
c. 2
d. 12

explain the formula : ) you.

Which describes a relationship based on the general theory of relativity?

Acceleration in space and magnetism on Earth have opposite effects on objects.Acceleration in space and magnetism on Earth have the same effects on objects.Acceleration in space and gravity on Earth have opposite effects on objects.Acceleration in space and gravity on Earth have the same effects on objects. 

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