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Approximately how high above the ground is a spherical projectile nine seconds after it has been launched straight up with an initial velocity of 60 m/s?
A. 11.1 m
B. 44.4 m
C. 138.2
D 320.7
In the answer explanation they find the time it takes for the projectile to reach its apex, which is six seconds, for a total flight time of 12 seconds. From their they conclude that the height at 9 seconds is equal to the height at 3 seconds. How did they figure that out based on this information? I know it is used to make the calculation easier. Either using t=3 or t=9 you get the same answer of 135. If this were on the MCAT I would have thought that I did the problem wrong because the calculation is not among the answer choice.
The first time I did this calculation I got the answer wrong because I had the equation as y=vt + 1/2at^2 instead of y=vt - 1/2at^2. Can someone explain the negative sign to me? I know that it is due to gravity.
A. 11.1 m
B. 44.4 m
C. 138.2
D 320.7
In the answer explanation they find the time it takes for the projectile to reach its apex, which is six seconds, for a total flight time of 12 seconds. From their they conclude that the height at 9 seconds is equal to the height at 3 seconds. How did they figure that out based on this information? I know it is used to make the calculation easier. Either using t=3 or t=9 you get the same answer of 135. If this were on the MCAT I would have thought that I did the problem wrong because the calculation is not among the answer choice.
The first time I did this calculation I got the answer wrong because I had the equation as y=vt + 1/2at^2 instead of y=vt - 1/2at^2. Can someone explain the negative sign to me? I know that it is due to gravity.