07

7.  The tension in the string AB is (pulley and string are massless)
(1)  15 N                                                          (2)  10 N
(3)  20 N                                                          (4)  30 N

From F.B.D of 1kg mass we get:-
    T + ma = mg
=>T+ a = 10  (becuase m=1kg) 
=>a=10 - T...eq;-(1)
From F.B.D of 3kg mass we get:-
T=Ma +Mg
a=(T-30)/3 (because m=3kg) ...eq(2)

from 1 and 2 we get:-
10-T = (T-30)/3
=>30-3T=T -30
=>4T=60
=>T = 15 N
So the correct option is (1)
not (4)


 

  • 2
What are you looking for?