A roller coaster car picks up speed as it rolls down the slope. As it starts down the slope, its speed is 4 m/s. It accelerates at a rate of 6 m/s2. What is its velocity after 3 seconds?

Ithink the answer is c. make unnecessarily  wide gestures 

Distance covered, s = 8ft - 4ft = 4 ftinitial velocity, u = 34 ft/sthe acrobat is moving upwards and therefore, a = -g = -9.81 m/s^2 = 32.19 ft/s^2applying equation of motion; s = ut -1/2gt^2then,4 = 34t -1/2*32.19t^24 = 34t - 16.095t^2rearranging; -16.095t^2 + 34t - 4 = 0solving the quadratic equation; t = {-34 +/- sqrt [34^2 - 4(-16.)]}/2(-16.095) = 1.06 +/- 0.93 = 0.13 or 1.99the acrobat will take 0.13 seconds to be at 8 ft above the ground. additionally, once at the maximum height, the acrobat will move down and be at the same spot (that is height) after 1.99 seconds moving down.

The disturbance in a transverse wave is perpendicular to the wave motion.unlike a transverse wave, the disturbance in a longitudinal wave is parallel to the wave motion (a), that is, back and forth.