I have a question. I have the answer of 2.5 kg but I dont understand how it is s

ID: 1468474 • Letter: I

Question

I have a question. I have the answer of 2.5 kg but I dont understand how it is solved.

The question is-

Two packages are connected by a very light string that goes over an ideal pulley as shown in

the figure. Package A has a mass of 3.0 kg and can slide along a rough plane inclined at 30°

above the horizontal. The string acts on package A parallel to the surface of the plane. The

coefficient of static friction between package A and the plane is 0.40. What minimum mass

should package B have in order to start package A sliding up the ramp?

Here,

let the second mass , m2 = 3 Kg

let the unknwown mass is m

for the block to just move

tension in the string = frictional force acting on 3 kg

T = m2 * g * sin(theta) + u * m2 * g * cos(theta)

m *g = m2 * g * sin(theta) + u * m2 * g * cos(theta)

m = 3 *(sin(30) + 0.40 * cos(30))

m = 2.54 kg

the mass needed is 2.54 Kg

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