Calculating velocity, accelerated motion

Please help with calculating the required numbers.

1) A car moves at 20ms/per second when he brakes. These brakes deliver 4g's in deceleration (4 x 9.8ms/s). Find the time to stop after applying the brakes.

2a) A child throws a ball up at an initial velocity of 49ms/s. How high will it go?

2b) How long will it take to reach this distance?

2c) A stone is thrown does a 500m cliff with a velocity of 49m/s ^-1. How long will it take to impact and how fast is it?

3) A car travels at 36km/h. He sees an obstacle and after a 0.2 sec reaction time, he decelerates at 20m/s ^(-2). What is the minimum stopping time?

4) A car travels at 20 m/s ^-1. He sees an obstacle 10m and reacts in 0.4 sec. He decelerates at 20m/s ^-2. Find:

a) The distance the car moves before he reacts

b) The distance the car moves during braking

c) The total stopping distance

5) A sprinter leaps from the starting block and reaches a velocity of 11m/s in 0.5 sec. If acceleration is uniform at the start, what is the acceleration?

Thank you.