Question

Block A, with a mass of 50 kg, rests on a horizontal table top. The coefficient of static friction is 0.40. A horizontal string is attached to A and passes over a massless, frictionless pulley as shown. The smallest mass mB of block B, attached to the dangling end, that will start A moving when it is attached to the other end of the string is

Answer 1

Thus the mass of block B is 30 Kg.

Explanation:

We are give that:

• Mass of block = 50 kg
• Coefficient of friction = 0.

Solution:

The horizontal forces on the 50 kg mass that just keep it from moving are

F - f =0

mg - uN = 0

m = uN/g

m = (.4)(50)(9.8)/(9.8) = 20 kg for static equilibrium

The mass of block B = Mass of block A - Mass of 20 kg

The mass of block B =  50 Kg - 20 Kg

The mass of block B = 30 Kg

Thus the mass of block B is 30 Kg.