a 1500 kg automobile is traveling up to 20 degree incline at a speed of 6 m/s if the driver wishes to stop his car in a distance of a 5m, determine the frictional force at pavement which must be supplied by rear wheels.
Sum work done and energies.
Frictional force = F N
Stopping Distance = D = 5 m
Speed uphill = v = 6 m/s
before braking:
KE=(1/2)mv^2
PE=0
W=0
after braking:
KE=0
PE=mg*Dsin(θ)
W=D*F
Equate KE+PE+W before and after braking, and solve for F.