- #1
nebullient
- 10
- 2
Homework Statement
A person standing at the top of a hemispherical rock of radius R kicks a ball (initially at rest on the top of the rock) to give it horizontal velocity ##v_i##. What must be its minimum initial speed if the ball is never to hit the rock after it is kicked?
Homework Equations
The Attempt at a Solution
##d_y = 1/2at^2##
##-R = -1/2gt^2##
##2R = gt^2##
##t = { \sqrt \frac {2R} {g}}##
##d_x = v_xt##
##d_x = v_it##
## v_i = \frac {d_x} { \sqrt {\frac {2R} {g}}}## If ##d_x = R##, then
##v_i = \frac {R} { \sqrt {\frac {2R} {g}}} = { \sqrt {\frac {Rg} {2}}} ## But since ##d_x > R##, ##v_i > { \sqrt {\frac {Rg} {2}}} ##However, the answer is just ##v_i > { \sqrt {Rg} } ##Please let me know where I went wrong.