p
Lv 4
p asked in Science & MathematicsPhysics · 9 years ago

Another physics K**LER prob?

A crate (A) of 13 kg on a frictionless inclined plane is attached to another crate (B) of 22 kg by a massless rope. The rope passes over an ideal pulley so that B is suspended in air. The plane is inclined at θ = 24.0°. Use conservation of energy to find how fast B is moving if after A has moved 1.4 m along the incline , starting from rest.

okay, this question has a picture that really doesn't give much info. It is a right triangle, A is on the hypotenuse, B is on the opposite or (vertical 90°), & θ = 24.0°.

the ans is roughly around 3.62 m/s, help me get to it

thanks

1 Answer

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  • DH
    Lv 7
    9 years ago
    Best Answer

    Use conservation of energy

    (K + U)1 = (K + U)2

    K1 = 0 and U1 = 0 (Set the initial position of each block to 0)

    Now U2 = mA*g*1.4*sin(24) - mB*g*1.4 and K2 = 1/2*mA*v^2 + 1/2*mB*v^2

    so 1/2*mA*v^2 + 1/2*mB*v^2 + mA*g*1.4*sin(24) - mB*g*1.4 = 0

    so v = sqrt(2*( mB*g*1.4 - mA*g*1.4*sin(24))/(mA + mB)) =

    v = sqrt(2*(22*9.8*1.4 - 13*9.8*1.4*sin(24))/(13 + 22)) = 3.62m/s

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