Hello! Thank you forum for providing help for my last thread :).(adsbygoogle = window.adsbygoogle || []).push({});

So far, have 2 more problems which I have some idea how to solve, but not enough to solve it.

1. The problem statement, all variables and given/known data

A stone is projected at an initial speed of 120 ft/s directed 62 degrees above the horizontal , at a cliff of height h. The stone strikes the ground 5.5 s after launching. Find the height of the cliff, the speed of the stone just before impact at A and maximum height H reached above the ground

Pretty much, its ball thrown from ground and landing at a cliff.

2. Relevant equations

3. The attempt at a solution

I think I did it, but im 100 % sure I got something wrong, heres what I did:

First I found V0y=v0 * sin 62 =32.3 m/s

Next I found the time, when the ball has reached its maximum height.

t=(v0y-Vy)/g=(32.3-0)/9.8=3.3 s

Found the max height

ymax=v0yt-(gt^2)/2=32.3 * 3.3 -(*0.5*9.8 * 3.3^2)= 53.229 m.

Now this is where I think I got it wrong.

Now we calculate the speed of the stone JUST BEFORE THE IMPACT at A.

We know that the time it took the stone to get from the maximum height to cliff is =5.3-3.3 = 2 s

V=-gt(because the velocity at the maximum height of the stone is 0)

V=-21.56 m/s

as we need speed, its absolute value aka =21.56 m/s

We found the speed of the stone, max height H, lets find how many meters did the stone travel from the maximum height to the cliff.

S(from max height to cliff)=gt^2 *0.5=4*0.5*9.8 = 19.6 m(cuz velocity at the maximum height is 0)

So thats it, answers are

S(from max height to cliff) =53.229-19.6=33.629 m

Speed is 21.56 m/s

S(max)=53.229 m

Where did I made a mistake? I know I did it somewhere because I missed something, help please!

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