# Homework Help: Determine max heigh above the ground reached by the marble

1. Jun 13, 2007

### t_n_p

1. The problem statement, all variables and given/known data

http://img253.imageshack.us/img253/4648/untitledfn3.jpg [Broken]

3. The attempt at a solution

I've done parts a and b succesfully, but am not sure how to do c.

Last edited by a moderator: May 2, 2017
2. Jun 13, 2007

### George Jones

Staff Emeritus
Using the ground as the zero for gravitational potential energy, what is the total energy of the marble at the instant of launch? What is its total energy when it's at maximum height h (not to be confused with H)?

3. Jun 14, 2007

### andrevdh

Using the know initial kinetic energy of the marble, $$E$$, and the launching angle, $$\theta$$, you can calculate the speed of the marble at top of its trajectory since at this point is has only a horizontal speed component, its vertical speed component is zero.

4. Jun 14, 2007

### t_n_p

I'm still not sure how to peice it all together. None of the formulas I am provided with seem to be relevant either! :yuck:

5. Jun 14, 2007

### andrevdh

The horizontal speed of a projectile is constant. It can be calculated from the initial speed and angle of the projectile (it is just the horizontal component of the initial velocity of the projectile). This horizontal speed will then remain the same throughout the lifetime of the projectile. So calculte it from $$E$$ and $$\theta$$.

I also tried to explain the 99% voltage a bit better in the RC question.

Last edited: Jun 14, 2007
6. Jun 14, 2007