1. ## kinetic energy

Okay so i'll go right to it (been sitting about 2 hours with this question);

An icecube is sliding 3 meters friction free off the ledge of a house roof which has the angle of 27 degrees. What speed will it attain at the edge of the roof?

Just imagine a triangle with the hyp of 3 meters and the angle at the edge is 27degrees. The one and only force that can meddle with the ice cube must be gravity (9.82m/s(square))

So please solve this for me so I can understand what im doing wrong.

I've got no clue where the 2 comes from...

2. Originally Posted by Hanga
Okay so i'll go right to it (been sitting about 2 hours with this question);

An icecube is sliding 3 meters friction free off the ledge of a house roof which has the angle of 27 degrees. What speed will it attain at the edge of the roof?

Just imagine a triangle with the hyp of 3 meters and the angle at the edge is 27degrees. The one and only force that can meddle with the ice cube must be gravity (9.82m/s(square))

So PLEASE for the LOVE OF GOD solve this for me so I can understand wtf im doing wrong.

I've got no clue where the 2 comes from...
Are you sure that v=square(2*9.82+3*sin(27))?

Using conservation of energy, the result seems to be:
$KE = PE \rightarrow \frac{1}{2}mv^2 = mgh$

$\frac{1}{2}v^2=gh$

$v = \sqrt{2gh} = \sqrt{2(9.81)(3)(sin27)}$

Alternatively, you can just use kinematics and the answer appears as clear as day:
$v_f^2 = v_0^2 + 2ax$ where $v_f, v_0, a, x$ are the final velocity, initial velocity, acceleration, and distance traveled, respectively.
$v_f^2 = 0 + 2(9.81sin(27))(30) \rightarrow v_f = \sqrt{2(9.81)(3)(sin27)}$

3. It looks like you are using the formula $v^2 = u^2 + 2as$, although I am not sure where you numbers have come from?

4. Originally Posted by craig
It looks like you are using the formula $v^2 = u^2 + 2as$, although I am not sure where you numbers have come from?
Oops, I meant 3 instead of 30 in
$
v_f^2 = 0 + 2(9.81sin(27))(30) \rightarrow v_f = \sqrt{2(9.81)(3)(sin27)}
$

5. Originally Posted by Last_Singularity
Oops, I meant 3 instead of 30 in
$
v_f^2 = 0 + 2(9.81sin(27))(30) \rightarrow v_f = \sqrt{2(9.81)(3)(sin27)}
$