Question

Block A (mass 40 kg) and block B (mass 80 kg) are connected by a string of negligible mass as shown in the figure. The pulley is frictionless and has a negligible mass. If the coefficient of kinetic friction between block A and the incline is μ_k = 0.24 and the blocks are released from rest, determine the change in the kinetic energy of block A as it moves from C to D, a distance of 19 m up the incline.
J

Answer 1

___________________________

Work done on A = change in KE of A

Thus, we can actually get just the work done on A.

For block A, the sum of forces is

T - m_A g sin37 - u_k m_A g cos 37 = m_A a

Plugging values in,

T - 311.05 = 40a ___ [1]

For block B,

m_B g - T = m_B a

Thus,

784 - T = 80a _____[2]

From equations 1 and 2,

a = 3.9413 m/s^2

Thus, as work on A = m_A a d = 40 x 3.9413 x 19 = 2.9954 x 10³ J

Work on A = change in KE of A = 2.9954 x 10³ J

___________________________

Please rate

if any mistake in this answer please comment i will clarify your doubt . thank you