Rough Surface with: Ms = 0.8 HK = 0.4 (a) Find the magnitude of the
force F needed to prevent the
book from sliding down the
rough wall.
F
M = 1.5 kg
600
(b) Find the minimum force F
needed to set the book in
motion up the rough wall with
constant velocity

I'll do it rn and then answer

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.