how long will it take to hit water and car's final velociety. 2 questions.?

Question

1) How long does it take for you hit the water if you drop off a high diving board which is 7.6 meters high?

2)What is your car's final velocity if you are initially going 6 m/s and then accelerate at 9.3 m/s2 for 0.60 seconds?

please solve them and explain how you solved.
Thanks

Answer 1

I 'm sure you were given a set (usually 4) of equations to use on this type of problem. How to know which to use? Take inventory of what you know and what you need to find. The variables of one of the equations should use what you know and the only other variable should be what you need. Just look over the equations in the set to find the one that fits your situation.

1) You know vertical distance, original velocity (zero), acceleration due to gravity, and you need to find the time to reach the water. Use y = Vo*t + (1/2)*g*t^2
where y is distance to the water, Vo=0 (diver just drops off the board), and g=9.8 m/s^2

2) Use Vf = Vo + a*t