A mass m1 = 3.9 kg rests on a frictionless table and connected by a massless str

Question

A mass m1 = 3.9 kg rests on a frictionless table and connected by a massless string over a massless pulley to another mass m2 = 5.8 kg which hangs freely from the string. When released, the hanging mass falls a distance d = 0.8 m. How much work is done by gravity on the two block system? J How much work is done by the normal force on m_1? J What is the final speed of the two blocks? m/s How much work is done by tension on M_1? J What is the tension in the string as the block falls? N The work done by tension on only m_2 is: positive zero negative What is the NET work done on m_2? J

Explanation / Answer

Acceleration of the blocks is a = m2 * g / (m1 + m2) = 5.8*9.8 / (3.9+5.8) = 5.86 m/s^2

(4)

Tension in the string is, T1 = m1* a = 3.9* 5.86 = 22.85 N = 22.9 N

(5)

The work done by the string is W = T1* d = 22.85 * 0.8 m = 18.3 J

(7)

The net work done on mass m2 is W = (m2*g - T1) *d

    W = (5.8*9.8-22.85) *0.8

W = 27.2 J

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