While a roofer is working on a roof that slants at 42.0 degrees above the horizontal, he accidentally nudges his 85.0N toolbox, causing it to start sliding downward, starting from rest.
If it starts 4.40m from the lower edge of the roof, how fast will the toolbox be moving just as it reaches the edge of the roof if the kinetic friction force on it is 20.0 N?
If it starts 4.40m from the lower edge of the roof, how fast will the toolbox be moving just as it reaches the edge of the roof if the kinetic friction force on it is 20.0 N?
-
Hello
the initial potential energy is mgh with h = 4.4*sin(42°)
Epot = mgh = 85.0*4.4*sin42 = 250.25 Nm
Assuming that the 20 N are the friction force on the incline, not on the horizontal.
The lost friction energy is Ff*s = 20*4.4 Nm = 88 Nm
Ekin = Epot - Efric
1/2 mv^2 = 162.25 Nm
v^2 = 2*162.25/(85/9.81)
v = 6.12 m/s <-- ans.
Regards
the initial potential energy is mgh with h = 4.4*sin(42°)
Epot = mgh = 85.0*4.4*sin42 = 250.25 Nm
Assuming that the 20 N are the friction force on the incline, not on the horizontal.
The lost friction energy is Ff*s = 20*4.4 Nm = 88 Nm
Ekin = Epot - Efric
1/2 mv^2 = 162.25 Nm
v^2 = 2*162.25/(85/9.81)
v = 6.12 m/s <-- ans.
Regards