A large boulder is ejected vertically upward from a volcano with an initial speed of 40.0 m/s. Ignore air resistance. (d) When is the velocity of the boulder zero?

Video transcript

welcome back everybody. We have a stone that is thrown directly upward. So I will plot its motion with this arrow and what goes up must come right back down. Now. We are told that it starts off with an initial vertical velocity of 10 m per second and at this highest point it's going to stop momentarily, meaning it will have a final Vertical velocity of 0m/s. Now, since this rock is in free fall, as we are ignoring wind resistance, its acceleration is going to be the acceleration due to gravity which is equal to negative 9.8. And we are tasked to find the time When velocity is equal to zero. Well, philosophy is equal to zero at this very, very top point. So this is going to be our time at the top of our motion. So for this we are actually going to use a condom. Matic formula and states that our final vertical velocity is equal to our initial vertical velocity plus our vertical acceleration times time. We know a lot of these values. So let's go ahead and plug those in. Final Vertical velocity is zero which is equal to our initial vertical velocity plus Our acceleration of negative 9.8 times. T go ahead and subtract -10. We're sorry 10 from both sides. And we are going to get that negative 10 is equal to negative 9.8 times T Dividing by -9.8. We get that T is equal to 1.02 seconds corresponding to our answer. Choice of the Thank you guys so much for watching. Hope this video helped, and we will see you all in the next one.