Determine max heigh above the ground reached by the marble

[t_n_p]

Homework Statement

http://img253.imageshack.us/img253/4648/untitledfn3.jpg

The Attempt at a Solution

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

 

[George Jones]

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)?

 

[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.

 

[t_n_p]

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.

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

 

[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.

 

[i.mehrzad]

What you can do is assume that zero potential level is height H.
with that as the initial stage and the highest point as the final stage conserve energy and the potential difference between the two stages will relate you to the height between the two stages.