Final answer:
The time taken by the jet ski to reach a final velocity of 70 m/s, accelerating from rest at 15 m/s², is approximately 4.67 seconds, which rounds to 5 seconds (option c).
Step-by-step explanation:
The student has asked how much time passed during the acceleration of a jet ski, which reaches a final velocity of 70 m/s from rest, given an acceleration of 15 m/s². To solve for time, we can use the kinematic equation which relates velocity, acceleration, and time:
v = u + at, where v is the final velocity, u is the initial velocity, a is the acceleration, and t is the time.
Since the jet ski starts from rest, the initial velocity u is 0. Rearranging the equation to solve for time gives us t = v/a. Plugging in the values, we get t = 70 m/s / 15 m/s² = 4.67 s. When rounding to the nearest second as per the multiple-choice options provided, the time is 5 seconds (option c).