Question

3. A block A of weight 40 N is placed on a table and another block B of weight 20 N
is hanging by a cord connected with block A over a frictionless, massless pulley as
shown in figure-2.
(a) Determine the minimum mass of block C to keep block A from sliding if the
static friction coefficient µs between A and the table is 0.20.
[4 marks]
(b) Find out the contact force of block C with block A.
[3 marks]
(c) Block C suddenly is lifted off from block A. What is the acceleration of block
A if the kinetic friction coefficient µk between the block A and the table is
0.15?

Answer 1

Answer:

f

2

=(1.40+4.20)μ

=0.3×5.6

=1.68N

Now,

mg=1.40N

f=μmg=0.3×1.40

=o.42N

T.f=0.42N

F=f

1

+T+f

2

=(0.42)2+1.68

=0.34+1.68

=2.52N

Hence,

optionBiscorrectanswer.

solution