Arock breaks loose from a cliff and plunges toward the ground 400 feet below. the distance "d" that the rock falls in "t" seconds is given by the equation d=16t^2. how long does it take the rock to hit the ground?

The distance the rock has to travel to hit the ground is 400ft.  
400 = 16 * t^2divide both sides by 16 and take the square root.  
25=t^2

5=t

Answer: d. 39 cmin the diagram, the approximate length of the minor arc de is 39 centimetres.step-by-step explanation: the formula for the length of an arc in a circle is as displayed below.let the length of the minor arc de = xx = 2( pi )r × angle of sector / 360°from this, we will substitute the values given from the problem into the formula to obtain the length of the minor arc de.x = 2( pi )r × angle of sector / 360°r = radius = 25cmpi as an approximate value = 3.14angle of sector = 120°x = 2( 3.14 )( 25 ) × 120° / 360°x = 157 × 1 / 4x = 39.25x = 39 ( rounded to the nearest whole number as an approximate value )