SOLUTION: When a body is projected vertically upwards with the velocity v=7m/s, the height s reached by the body after time t secs is given in meters by the formula S=7t-4.9t^2. Find the gre

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Question 861543: When a body is projected vertically upwards with the velocity v=7m/s, the height s reached by the body after time t secs is given in meters by the formula S=7t-4.9t^2. Find the greatest height to which the body will rise and the time taken.
Please help me, I will really appreciate it. Thanks
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
S=7t-4.9t^2
The precalculus solution is to graph the equation
+graph%28+300%2C+200%2C+-4%2C+4%2C+-3%2C+3%2C+-4.9x%5E2+%2B7x%29+
from the graph we see t = 0.7 seconds and the max height is 2.5 meters
the calculus solution is to take the first derivative and set it = 0
S' = 7 - 9.8t
7 - 9.8t = 0
9.8t = 7
t = 7/9.8 = 0.71
then substitute for t in orignal equation
S = 7*(0.71) - 4.9*(0.71)^2
S = 2.5