Alittle boy is standing at the edge of a cliff 1000 m high. he throws a ball straight downward at an initial speed of 20 m/s, and it falls straight down to the ground below. at a time of 6 seconds after it was thrown, how far above the ground is it? the acceleration due to gravity is 10 m/s2 .

The ball will be at 700 m above the ground.

Explanation:

We can use the following kinematic equation

.

where y(t) represent the height from the ground. For our problem, the initial height will be:

.

The initial velocity:

,

take into consideration the minus sign, that appears cause the ball its thrown down.  The same minus appears for the acceleration:

So, the equation for our problem its:

.

Taking t=6 s:

.

.

.

.

.

So this its the height of the ball 6 seconds after being thrown.

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more