# More Physics Confusion

Discussion in 'General Off-Topic Chat' started by jonthedit, Oct 20, 2014.

# More Physics Confusion

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Member
May 30, 2011
To find the initial velocity of this, what do I need to do?
Ignoring Air resistance and Air Friction:

I have found t, the total time it takes to reach the water, and the height maximum point, when the Vi = 0.
I am lost how to find the initial velocity.

I have tried

deltaX
/ = v
t

,

trying: 16.05 / 2 (the current t) = 8.025m/s

I have tried finding t for the triangle part I made only, being sqroot of (8.03/5).
This makes the Vi = 12.6649m/s, which I think is too big of a number :|

Finally, taking the total Xx distance, 13.9[total Xx]/2[original t]: I get Vi=6.95

Member
May 7, 2011
Québec

BORTZ likes this.

Member
May 30, 2011
That has to do with...?
Also in this problem I get to assume gravity is 10m/s^2.

I just care about my initial velocity. Gravity should not matter to find this... right?

Member
May 7, 2011
Québec
he's diving, he obviously ain't gonna fly 8m high in the sky then hit a wall and fall straight into the water.
it's a parabolic movement, the horizontal movement is constant, and the vertical is accelerated.

BORTZ likes this.

Member
May 5, 2013
You said you already know how long it takes for him to hit the water, no? We'll call that t1. So then your initial velocity in the X direction = 13.9/t1. From there, you should be able to do trigonometry with the angle of the dive.

Member
May 30, 2011
I said that too, but with the math it does not matter.
I am ignoring air resistance and friction. For purposes of equations, I can assume he hits a wall, because I do not care about his Xy descent, as I already know the change in Xy.
The 30* angle and unknown speed provided will make it a superhuman jump and his speed is going to be ridiculous.

Member
May 7, 2011
Québec

Member
May 30, 2011

9. ### VehoThe man who cried "Ni".

Former Staff
Apr 4, 2006
Zagreb
The correct solution is Vi=6,34 m/s

Plug it back into the projectile motion formulae and all the numbers fit.

ßleck likes this.

Member
May 30, 2011

Still not following this... I don't get how I find V0, I get V0y and V0x