pureouchies4717
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Johnny jumps off a swing, lands sitting down on a grassy 20 degree slope, and slides 3.5 m down the slope before stopping. The coefficient of kinetic friction between grass and the seat of Johnny's pants is 0.5.What was his initial speed on the grass?
now i know the answer is 2.96m/s, but i don't know how to get at it...heres what i tried:
Fn= mgsin20
Ff=.5mgcos20
mgsin20-Ff= ma
mgsin20- .5mgcos20 = ma
(m's cancel out)
a=2.88 m/s^2
Vi^2= 0 + 2(-2.88)(3.5)
Vi= 4.49 m/s
but this is definitely wrong... how do i get the real answer?
now i know the answer is 2.96m/s, but i don't know how to get at it...heres what i tried:
Fn= mgsin20
Ff=.5mgcos20
mgsin20-Ff= ma
mgsin20- .5mgcos20 = ma
(m's cancel out)
a=2.88 m/s^2
Vi^2= 0 + 2(-2.88)(3.5)
Vi= 4.49 m/s
but this is definitely wrong... how do i get the real answer?
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