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kathyt.25
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Homework Statement
(a) A skier is gliding at 6.75m/s on horizontal, frictionless snow. He starts down an 11deg incline. His speed at the bottom is 21.7m/s. what's the length of the incline?
(b) How long does it take him to reach the bottom?
I just need help with part (b)
Homework Equations
a = delta_v / delta_t
d=0.5(vf+vi)t
The Attempt at a Solution
From part (a), I figured out that a=1.67m/s/s: a=gsin(theta)=1.87m/s/s
For part (b), how do I know what kinematics equation to use?
1 - If I use t = vf-vi /a = 7.99s, I get the correct answer.
2 - If I use d=0.5(vf+vi)t, t = 144/0.5(21.7+6.75) = 10.12s, I get the wrong answer.
How do I know which equation to use in kinematics problems? All pieces of information are available!