1. If the end of the ruler length 1 m is raised by 25 cm, the wooden bar is sliding down at the constant speed. What is the acceleration of the bar if the height of the end is increased twice?

Answer 1

tan A = 0.25/1 = 0.25
A = 14 deg
normal force = W cos 14
friction force = mu W cos 14 = weight component down slope =W sin 14
for constant speed:
mu W cos 14 = W sin 14
or
tan 14 = mu = 0.25
then
at tan A = 0.50, then A = 26.6
friction force up slope = mu W cos 26.6
weight component down slope =W sin 26.6
so
mg sin 26.6 - .25 mg cos 26.6 = m a