- #1
charan1
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Homework Statement
You and your friend Peter are putting new shingles on a roof pitched at 22 degree . You're sitting on the very top of the roof when Peter, who is at the edge of the roof directly below you, 5.0 m away, asks you for the box of nails. Rather than carry the 2.5 kg box of nails down to Peter, you decide to give the box a push and have it slide down to him.
If the coefficient of kinetic friction between the box and the roof is 0.53, with what speed should you push the box to have it gently come to rest right at the edge of the roof?
Homework Equations
Vf^2=Vi^2+2*a*delta s
F=ma
The Attempt at a Solution
First found the length of the roof by assuming that the height was 5m and angle 22* i found the length to be 13.3475meters using trig...sin(22)=5m/roof length
then i did the force calculations to find Fnet then find the acceleration:
9.8cos(22)*2.5kg=22.71N
9.8cos(22)*2.5kg*.53= -12.039N
Fnet=22.71-12.039N
Fnet=10.671N
Then solved for the acceleration:
F=ma
10.671N=2.5kg * a
a=4.2684m/s^2
then i plugged those values into this equation to find Vi
Vf^2=Vi^2+2*a*delta s
0=Vi^2 + 2 * (4.2684m/s^2) * (13.3475m)
Vi=10.67m/s
is this correct? thank you!