- #1

chromechris1

- 4

- 4

- Homework Statement
- A person stands on top of a 45-m cliff and throws a 500-gram rock forward with a speed of 40 m/sec. What is the speed of the rock when it hits the ground. Solve using energy and using kinematic equations.

- Relevant Equations
- kinematic equations

Hi, so I solved this using energy. I also tried solving this using kinematic equations. The issue I am running into s for calculating the Vy of the problem. I am able to find the time it takes the rock to fall using d=(1/2)gt^2. Then, I considered two different ways of going about finding the Vy. I can simply: Vy=gt. But then I also remembered that V=(d/t). So then I tried V=45/3 (I am using g=10m/s^2). The first formula yields the correct answer, but the second does not. Why is it that I cannot use the second formula if it is true that V=(d/t). My guess would be that it is because in the formula V=(d/t), we are considering calculating a constant velocity but in the second formula we are calculating velocity as a result of acceleration? Thank you for any insight into this.