Do not round intermediate answers. Give your final answer(s) to three decimal pl
ID: 1779490 • Letter: D
Question
Do not round intermediate answers. Give your final answer(s) to three decimal places. Check your units The flatbed truck starts from rest on a road whose constant radius of curvature is 28 m and whose bank angle is 11°. If the constant forward acceleration of the truck is 2.5 m/sec2, determine the smallest time t after the start of motion at which the crate on the bed begins to slide. The coefficient of static friction between the crate and truck bed is ,-0.8, and the truck motion occurs in a horizontal plane. t= 17.194 × secExplanation / Answer
for crate to slide it has to overcome friction force
this friction force can be overcome by the centripetal force
centripetal force = mv^2 / r
so,
mg * sin(11) + k * (mg * cos(11) + mv^2 * sin(11) / r) = mv^2 * cos(11) / r
g * sin(11) + k * (g * cos(11) + v^2 * sin(11) / r) = v^2 * cos(11) / r
9.8 * sin(11) + 0.8 * (9.8 * cos(11) + v^2 * sin(11) / 28) = v^2 * cos(11) / 28
v = 17.975 m/s
by first equation of motion
v = u + at
since the truck started from rest so
17.975 = 0 + 2.5 * t
t = 7.19 sec
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