Kinematics to the millionth POWER

[DaMastaofFisix]

Okay, here's yet another headache waiting to happen:

Galileo is atop the leaning tower of pisa,at a Height H. he throws down a cannonball with an initial velocity Vo, while his buddy down below throws another cannonball with initial velocity 2Vo at the bottom of the tower.

a) in terms of Vo and H, at what time does the collision occur?

*When the cannonballs collide, Galileo's cannonball has 7 times the velocity of his buddy's

b) in terms of H only, at what height does the collision occur?

I used kinematics for both of them and kinematics only. for part a, I got H/(3Vo), and for b I got H/4. Are these answers good and if not, should I be introducing like conservation of energy?... Thanks a bunch for anyone brave enough to step up to the challenge.

 

[siddharth]

Yep, your answers are correct.
This problem is not at all tough. How did you do it? Did you use the relative displacement to find the time? That really simplifies your calculations as the relative acceleration will be 0.

 

[DaMastaofFisix]

Thanks for the conformation. Indeed my asnwers were correct, as my professor pointed out. I disd't use relative motion in any of the equations, just simple kinematic rearrangement. I used the displacement equation and the velocity equation with time (the first derivative of the displacement equation) and used what was given to equate the positions and velocities of the cannonballs. Once again, thanks for helping a physics student in distress.