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Finding initial velocity given angle, friction, and distance 
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#1
Oct2510, 08:26 PM

P: 9

1. The problem statement, all variables and given/known data
Johnny jumps off a swing, lands sitting down on a grassy 20 degree slope, and slides 3.5m 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? 


#3
Oct2510, 08:33 PM

P: 9

I know that because it is on a slope, n should equal mgcos20, but I am very confused because I dont know what the mass of Johnny is. 


#4
Oct2510, 08:35 PM

PF Gold
P: 712

Finding initial velocity given angle, friction, and distance



#5
Oct2510, 08:40 PM

P: 9




#6
Oct2510, 08:45 PM

PF Gold
P: 712




#7
Oct2510, 08:54 PM

P: 9

[tex]\sum[/tex]F_{y}=nmgcos20=0 


#8
Oct2510, 09:01 PM

PF Gold
P: 712

N = mgcos20^{o} F_{k} = μ_{k}mgcos20^{o} substitute that to your ΣF_{x} equation and solve for a_{x}: ΣF_{x} = ma_{x} = mgsin20^{o}  μ_{k}mgcos20^{o} You see how the mass cancels out? 


#9
Oct2510, 09:09 PM

P: 9




#10
Oct2510, 09:10 PM

PF Gold
P: 712

Just wondering, which part exactly were you stumped with? 


#11
Oct2510, 09:19 PM

P: 9




#12
Oct2510, 09:23 PM

PF Gold
P: 712

Anyways I'm glad everything worked out well for you 


#13
Oct2510, 09:33 PM

P: 9




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