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!

 

[Nate810]

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.

 

[Moetasim]

I would approach this problem by first identifying the given information and the unknowns. We are given the distance (1.40 m) and speed (1.50 m/s) of the more massive block, as well as the total mass of the two blocks (18.0 kg). Our unknowns are the mass of the more massive block (A) and the mass of the lighter block (B).

To solve for these unknowns, we can use the conservation of energy principle, which states that energy cannot be created or destroyed, only transferred from one form to another. In this case, the initial potential energy (U) of the system is converted into kinetic energy (K) as the blocks descend. We can use the equation K = (1/2)mv^2 to calculate the kinetic energy of each block.

Since the more massive block starts from rest, its initial kinetic energy is zero. Therefore, all of its initial potential energy must be converted into kinetic energy at the bottom. This means that its final kinetic energy (1/2)mA(1.50 m/s)^2 must be equal to its initial potential energy mAg(1.40 m), where g is the acceleration due to gravity (9.8 m/s^2).

We can set up a similar equation for the lighter block, but since it starts from a height of 1.40 m, its initial potential energy is not zero. Therefore, we can use the total mass of both blocks (18.0 kg) to calculate its initial potential energy (U = mBg(1.40 m)). Setting this equal to its final kinetic energy (1/2)mB(1.50 m/s)^2, we can solve for the mass of the lighter block (B).

To solve for the mass of the more massive block (A), we can use the fact that the total mass of both blocks is 18.0 kg. Therefore, A + B = 18.0 kg. We can substitute the value of B that we calculated in the previous step and solve for A.

Using these equations and calculations, we can determine the mass of the more massive block (A) and the mass of the lighter block (B). It is important to note that in this problem, we have assumed that all of the energy is conserved and there is no energy lost due to friction or other factors. In reality, there may be some