Question

A body of mass 10 kg is to be raised by a massless string
from rest to rest, through a height 9.8 m. The greatest rtension
which the string can safely bear is 20 kg wt. The least time of
ascent is:
A. 2 s
B. 3s
C. 4s
D. none of these​

Answer 1

Answer:

The answer is option (d): None of these

Explanation:

A(max)=(T-mg)/m

          =g

during half time,body is accelerated from rest and during next half time deceleratees with same magnitude and comes to rest.

h/2=1/2*t12​*amax

->>t1 = 1sec