A brick is dropped (zero initial speed) from the roof of a building. The brick strikes the ground in 1.90 s. You may ignore air resistance, so the brick is in free fall. (b) What is the magnitude of the brick's velocity just before it reaches the ground?

Video transcript

So in this problem stone is dropped from the top of the tower. Stone hits the ground in 3.80. Sounds is neglected. So the stone is falling under the influence of gravity. What is the stone speed as it touches the ground? The problem really only gives us T equals 3.80 seconds. We also know that consistently fall. The acceleration is just the acceleration of gravity on Earth, which is negative 9.81. Because for simple swim. And we also know since it's dropped from the top of the tower, no initial velocity that we I. Is equal to 0m/s. So we can start off by writing the kinetic equations which we call the F. B. I. Plus 50 squared goes the I squared 1-8. Other act delta X. Who's the I. C. Just want to have a T. Square given these parameters and we want to find the F. See that the easiest creation to use just one. Since we have t. We have egg, you know the B. I. Zero. So from one the F. Is equal to B. I. G. In this case times two we know that B. I. Zero. So we can substitute the values for G. M. T. To directly solve for you know that G is just squared A. T. is 3.8 was supposed Let me get that b. 37.2 meters per second. Now since it's asking for speed, it's just the positive value. Speed is just a magnitude of philosophy. So the answer choice is B. of this house.