The mass of Trevor's head is 5 kg and its centre of mass (A) is located LHead = 30 mm anterior to the axis of rotation (atlanto-occipital joint, B) acting at an angle of 90°. The neck extensors act LNeck = 52 mm posterior
to the axis of rotation, at an angle of 0 = 128º. Trevor is currently holding his head still. How much force do the
neck extensor muscles need to produce to keep the head from nodding (i. e. keep his head still). Assume
gravity is 9.8 m. s??
A
LNeck
LHead
ө
B
90°

Liquid. good luck : )

Answeroutward from: source;

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.