Manuel wants to determine how fast a toy car will move across different surfaces. he lines 3 ramps with different surface covers including wax paper, sandpaper, amd smooth carpet and runs the same car down each ramp to determine how long it takes for the car to reach the bottom. what is manuel's independent variable in this experiment?

Global warming was a major concern some people do not care global warming is fake it is not real the percentage of it happening  is slight 

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