Two blocks with different mass

[annabelx4]

Two blocks with different mass are attached to either end of a light rope that passes over a light, frictionless pulley that is suspended from the ceiling. The masses are released from rest, and the more massive one starts to descend. After this block has descended a distance 1.40 , its speed is 1.50 .

A. If the total mass of the two blocks is 18.0 , what is the mass of the more massive block?

B. What is the mass of the lighter block?

I know we probably have to use K_1 + U_1 + W_other = K_2 + U_2 but I'm not sure how so ..

Please help me!

 

[member 553083]

A. The mass of the more massive block can be determined using the equation, K_1 + U_1 + W_other = K_2 + U_2, where K is kinetic energy, U is potential energy and W_other is work done by other forces. We can assume that the total initial potential energy (U_1) is 0. We can also assume that the initial kinetic energy (K_1) is 0. The work done by other forces (W_other) is the same on both sides of the equation, so it cancels out. Therefore, we can rearrange the equation to solve for the mass of the more massive block:Mass = K_2/g*hwhere g is the acceleration due to gravity and h is the height of the more massive block after descending a distance of 1.40 m.Plugging in the given values, we get:Mass = (1.50^2)/(9.8*1.40) = 11.2 kgTherefore, the mass of the more massive block is 11.2 kg.B. The mass of the lighter block can be determined by subtracting the mass of the more massive block (11.2 kg) from the total mass (18.0 kg).Therefore, the mass of the lighter block is 6.8 kg.