An object, previously at rest, slides 5 m5m down a ramp, with an incline of pi/3 π3, and then slides horizontally on the floor for another 2 m2m. If the ramp and floor are made of the same material, what is the material's kinetic friction coefficient?
1 Answer
(I really want someone to double check my work since this is one of my first physics answers)
Explanation:
Let's use the top of the ramp for initial condition and bottom of the ramp for final condition.
PE_i + KE_i = PE_f + KE_f + W_"fric"PEi+KEi=PEf+KEf+Wfric
We know that:
Deltay = 5m(sin(pi/3)) = (5sqrt3)/2
KE_i = 0
PE_i = mgDeltay = (5sqrt3mg)/2
PE_f = 0
W_"fric" = 5mu_kF_N = 5mu_kmgcos(pi/3)= 5/2mu_kmgcolor(white)"-"
So our equation becomes:
(5sqrt3mg)/2 = KE_f + 5/2mu_kmg
We can also have another point (
PE_f + KE_f = PE_"f2" + KE_"f2" + W_"fric2"
KE_f = 2mu_kmg
Substituting this into the first equation gives:
(5sqrt3mg)/2 = 2mu_kmg + 5/2mu_kmg
(5sqrt3)/2 = 9/2mu_k
mu_k = (5sqrt3)/9 = 0.9622
Final Answer