SOLUTION: A rock is thrown upward with a speed of 48 feet per second from the edge of a cliff 400 feet above the ground. What is the speed of the rock when it hits the ground? Use accelerati

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Question 1119907: A rock is thrown upward with a speed of 48 feet per second from the edge of a cliff 400 feet above the ground. What is the speed of the rock when it hits the ground? Use acceleration due to gravity as -32 feet per second squared.
Found 2 solutions by solver91311, ikleyn:
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!




You want to solve for when where and

Plug in the numbers and solve the quadratic. The answer will be the positive root.


John

My calculator said it, I believe it, that settles it

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
In Physics, the students solve this problem by applying the Energy Conservation  Law


%28m%2Av%5E2%29%2F2 + m%2Ag%2AH = %28mV%5E2%29%2F2,


where m is the mass of the body, v is the starting velocity (directed vertically up),  V = the final velocity directed 
vertically down (the value under the question) and g = 32 ft/s^2 given in the condition.


Canceling "m" in both sides and simplifying, you get


V = sqrt%28v%5E2+%2B+2%2Ag%2AH%29 = sqrt%2848%5E2+%2B+2%2A32%2A400%29,


and what you need to do is to use your calculator.