A tennis ball on Mars, where the acceleration due to gravity is 0.379g and air resistance is negligible, is hit directly upward and returns to the same level 8.5 s later. (b) How fast was it moving just after it was hit?

Video transcript

Hello everyone. So in this problem, a stone on earth where the acceleration due to gravity is G. Is thrown vertically upward by an astronaut so that it returns to its starting point after seconds. What is the speed at which the stone was thrown by the astronaut? So we have some astronaut and he throws a stone upwards with some initial velocity which we want to find undergoes freefall. We're just some maximum heart And the total time is 10 seconds. And we also recall that the time taken as it was thrown to reach, its maximum height would just be half of this total time. It would be five seconds. And then the time taken from the maximum height to the original height would be the other five seconds. And since it is in free fall It undergoes an acceleration of negative 9.81 m/s squared. We recall the Kitimat equations as VF I plus 80. The second one which is V F squared is equal to V I squared plus two A delta X. And the 3rd 1 delta X. Is equal to the I. T. Plus one half a T squared. So in this problem were given some time and were given some acceleration and we want to find B. I. And we notice that we don't have necessarily delta X. But we know at this h max VF 0 - zero m/s. So we do have V. F. For this first half traveled, which is why we had to make this important distinction that the time taken from this original position to this age max is just half of the total time you're a kid. So we can use this first chemical equation solvent B. I. You can rewrite it as V. F is equal to V. I plus G. T. And we know that B. F. There's simply zero. So now we can solve for the eye negative V. I. Is equal to G. G times T. And so we get that V. I. Is equal to 9.81 m/s squared, since the negative cancels times the half time. Finally, v. I. is equal to 49 m/s. Just answer choice. C. Of those hopes have a great time.