In the Figure the pulley has negligible mass, and both it and the inclined plane are frictionless. Block A has a mass of 1.3 kg, block B has a mass of 2.7 kg, and angle è is 26 °. If the blocks are released from rest with the connecting cord taut, what is their total kinetic energy when block B has fallen 27 cm and in ths block b is hanging down? i jus wanted to ask that difference PE=final KE means
mass of a*g*h-mass of b*g*hsin26=totalKE. is this right? bcause i m nt getting right answer. for a height should be h= 0.27cos26 and for b height=0.27?
PE=final KE
Means that the change in potential energy of the masses has to equal the final gain of kinetic energy of the masses.
On the second question, the formula is right, however, not having the figure, I have no idea what the h is. You need to go back to my original assumptions about the figure was, and see if that matches the figure. I am not a mindreader.
To find the total kinetic energy when block B has fallen 27 cm and block B is hanging down, you can use the conservation of energy principle.
According to the principle of conservation of energy, the total mechanical energy (potential energy + kinetic energy) of a system remains constant if no external forces are acting on it.
In this case, the potential energy at the initial position is converted into kinetic energy as the blocks move.
Let's break down the problem step by step:
1. Calculate the potential energy at the initial position for each block:
The potential energy for block A is given by: PE_A = m_A * g * h_A
The potential energy for block B is given by: PE_B = m_B * g * h_B
The height for block A, h_A, can be calculated as: h_A = h * cos(θ)
The height for block B, h_B, can be calculated as: h_B = h
Given that h = 0.27 m and θ = 26°, you can substitute these values to find h_A and h_B.
2. At the final position, all the potential energy is converted into kinetic energy.
Therefore, the total initial potential energy (PE) is equal to the total final kinetic energy (KE):
PE_A + PE_B = KE_total
3. Substitute the potential energy expressions and solve for KE_total:
(m_A * g * h_A) + (m_B * g * h_B) = KE_total
Remember to convert the angles from degrees to radians if your equations require it.
By following this approach and correctly substituting the values, you should be able to find the correct answer.