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Homework Statement
A disc is thrown at a 28° angle to the ground. It landed 39.8m away.
a) What is the velocity of the disc?
b) How long was the disc in the air?
Homework Equations
##θ = 28°##
##\vec{Δd}_H = 39.8 m [F]##
The Attempt at a Solution
a) I was thinking I should use the equation ##\vec{Δd}_H = \vec{v}_H Δt##. I of course don't have a time or horizontal velocity to work with, but what I do have is that :
##\vec{v}_H = \vec{v}_R cos(θ)## and subbing back I get ##\vec{Δd}_H = \vec{v}_R cos(θ) Δt## ( Note vR is the resultant velocity ).
Now as for ##Δt##, I want to replace it with ##\frac{2 \vec{v}_R sin(θ)}{\vec{a}}## as I can work with it.
So plugging back into my equation a second time and moving things around a bit I get :
##\vec{v}_{R}^{2} = \frac{ (39.8)(9.8) }{ (1.76)(sin(28°)) }##
##∴ \vec{v}_{R} = 22 m/s##
b) I simply use ##Δt = \frac{2 \vec{v}_R sin(θ)}{\vec{a}}## and I get ##Δt = 2.1 s##.
Part a) is the one I'm concerned with. Hopefully it looks okay.
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