# A force problem that seems easy but hard

by cy19861126
Tags: force
 P: 69 A 2.00-kg aluminum block and a 6.00-kg copper block are connected by a light string over a frictionless pulley. The two blocks are allowed to move on a fixed steel block wedge (of angle 30.0) as shown in Figure P4.53. Making use of Table 4.2, determine (a) the acceleration of the two blocks and (b) the tension in the string. My work so far: For the aluminum block - I got T = 2a, which I cannot solve For the copper block - I got Tx-58.8sin(30) = 6a - this is for x direction and Ny-58.8cos(30) = 6a - this is for y direction 58.8 is the weight force, which comes from 6*9.8 = 58.8N T = tension force N = Normal force All the equations won't get me to solve for acceleration for either blocks Thanks~~ If you cannot see the attachment, you may click here Attached Thumbnails
 P: 135 You don't need an x for the direction of T for the copper block since you are resolving it along the surface of the plane. Once you get this, its semple simultaneous equations.
P: 69
 Quote by QuantumCrash You don't need an x for the direction of T for the copper block since you are resolving it along the surface of the plane. Once you get this, its semple simultaneous equations.
I see what you are saying, but for the copper block, I defined the x axis to be the the ramp. Therefore, the coordinate diagram is a slanted one, not a standard one. As a result, you need Tx

P: 312

## A force problem that seems easy but hard

Neither block is accelerating in the y as you have defined it. Tension is purely in the x. You then get 2 equations with 2 unknowns because the tensions and accelerations are equal
 P: 135 If I get what you mean, you should not do that becaus you would need to take into account the normal force.

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