Batman find himself in a fault on a high ledge. in an attempt to trap him the jo
ID: 1353170 • Letter: B
Question
Batman find himself in a fault on a high ledge. in an attempt to trap him the joker runs out of the vault while the door closes. Batman fires a grappling hook into the ceiling at an angle, theta, attached to a line of length, L, and manages to pull himself off the ledge swinging down to the floor below. at the ver bottom of the swing he lets go of the line to the grappling hook in an attempt to slide the rest of the way out of the door. Find an equation for how far batman slides, x, as a function of L, theta, and uk, the coefficient between batman and the floor. If the door is 6.00 meters away from the bottom of the swing and the length of the line is 3.00 meters, the angle 70 degress and the uk .250 did batman make it out? if he did how fast was he sliding when he went through the door?
Explanation / Answer
here,
let the speed of Batman at the bottom be v
using conservation of energy
0.5 * m * v^2 = m * g * L * ( 1 - cos(theta) )
v = sqrt( 2 * g * L * ( 1 - cos(theta))
the accelration due to friction , a = - uk * g
v^2 - u^2 = 2 * a*x
x = ( 2 * g * L * ( 1 - cos(theta)) /( 2 * uk *g)
x = ( 2 * L * ( 1 - cos(theta)) /( 2 * uk )
the expression for x is x = ( 2 * L * ( 1 - cos(theta)) /( 2 * uk )
L= 3 m , theta = 70 degree , uk = 0.25
then x = ( 2 * 3 * ( 1 - cos(70)) /( 2 * 0.25 )
x = 7.9 m
the door is 6 m from the bottom , so ,
he made it out
let his speed at the door be u
using third equation of motion
u^2 - ( 2 * g * L * ( 1 - cos(theta)) = - 2 * ( uk * g) * ( 6)
u^2 - ( 2 * 9.8 * 3 * ( 1 - cos(70)) = - 2 * ( 0.25 * 9.8) * ( 6)
u = 3.05 m/s
the speed of Batman when he went through the door is 3.05 m/s
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