A student stands at the edge of a cliﬀ and
throws a stone horizontally over the edge with
a speed of 18.9 m/s. The cliﬀ is 77.2 m above
a ﬂat, horizontal beach. At impact, what is its speed?
I calculated the time it takes to reach the bottom, which was 3.967~ seconds. I figured the speed would just be 18.9 m/s, the same as the original speed, but something tells me that's not right. Can someone point me in the right direction please?
Stacey Warren - Expert brainly.com
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the horizontal speed would be 18.9m/s .. the vertical speed initially is 0.. due to gravity there will be some final vertical velocity. find that and then vector sum it..
I'm not sure how to vector sum, this is my 2nd week of physics. But I think I would take the 18.9 and just add it to the gravity, which is usually 9.81, so would it just be the sum: 28.71, or would i subtract them? I honestly am not sure...
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umm what you gotta do is find the final vertical velocity using v^2-u^2=2as.. here u is the initial velocity which is equal to zero.. so v^2=2as=2*10*77.2.. let this be equal to X^2.. and let the final horizontal velocity be equal to Y. you know this is equal to 18.9.. find Y^2
now the final vertical velicty and the final horizontal velocity are perpendicular to each other.. to find a resultant.. you do this.. sqrt(X^2 + Y^2).. this gives you the answer..
Alright, so bear with me, the equation should be
18.9 = sqrt(x^2+y^2)
18.9 = sqrt(39.29^2+y^2)
357.21 = 1543.999968 + y^2
-1186.799968 = y^2
-34.449963 = y, which is the speed in m/s?
no no no.. you have to find sqrt(x^2 + y^2).. you already have the value of y^2.. which is equal to v^2.. the final vertical velocity..
so the answer would be... sqrt [ 18.9^2 + (2*10*77.2) ]
Alright, I solved for that and got 43.60286688. But it says it's wrong.
43.247.. is that the answer?
Ah! It was right, it was just an error in the online program. I cannot thank you enough for your help:)