Question

Find the minimum weight of block A in order for motion to be impending down the plane (to the left). Assume the pulley to be frictionless. Given: WB = 275 lbs, θ = 35 °, μ = 0.25 for all surfaces.

Answer 1

88.25lbs

Step-by-step explanation:

Let N be the minimum weight to be found.

firstly we have to solve for the force body diagram for both blocks, for block B which is stable, we have its weight acting downwards,for it to move left affected by block A it would need a horizontal component which is the frictional force and we can calculate it as weight of B x coefficient of friction= 275lbs x 0.25 = 68.75lbs.

Calculating same for block A:(free body diagram)

the horizontal and vertical component of the forces on A would be:

Nsin35(horizontal comp) + Ncos35(0.25)(vertical comp)= 68.75lbs

=0.574N+0.205N=68.75lbs.

solving the above equation and making N subject of formula would result to 88.25lbs.