Question

A ball is dropped from a height of 20m. If its velocity increases uniformly at the rate 10m/s2 with what velocity and after what time will it strike the ground?

Answer 1

Answer: 2 seconds

Explanation:

Answer 2

Since I've only memorized a couple of formulas for these things, I need to do the time first:

I'll use the formula  Distance = (1/2) (acceleration) (time)²

20 m = (1/2) (10 m/s²) (time)²

Time² = (20 m) / (5 m/s²)

Time² = 4 sec²

Time = 2 seconds

Now ...

-- When the ball hits the ground, it has been falling for 2 seconds.

-- Its acceleration has caused its speed to increase by 10 m/s every second.

-- So after 2 seconds, its speed has grown to (2 s) (10 m/s²) = 20 m/s .