Question

Two mass m and 2m are attached with each other by a rope passing over a frictionless and massless pulley. If the pulley is accelerated upwards with an acceleration ‘a’, what is the value of T?
(a) $\frac{g+a}{3}$
(b) $\frac{g-a}{3}$
(c) $\frac{4m(g+a)}{3}$
(d) $\frac{m(g-a)}{3}$

Answer 1

I think option d... whether right

Answer 2

Answer:

(4/3)mg

Explanation:

According to the concept of Atwood machine.

For mass m, the forces are given as

T - mg = ma  -- 1

Similarly, for mass M, the forces are given as

2Mg - T = 2Ma --2

Adding equation (1) and(2),we get

3ma=mg. Thus,

a = mg/3m =g/3 -- 3

General formula = a=[(m1-m2)/(m1+m2)]g -- 4 ( m1>m2 )

The tension in the string can be found by substituting for a in equation (1) and making T as subject. Therefore,

T=mg/3+mg

= (4/3)mg

Thus, If the pulley is accelerated upwards with an acceleration ‘a’, what is the value of T will be (4/3)mg