Question
Physics Question on work, energy and power
Three masses M = 100 kg, m1 = 10 kg and m2 = 20 kg are arranged in a system as shown in figure. All the surfaces are frictionless and strings are inextensible and weightless. The pulleys are also weightless and frictionless. A force F is applied on the system so that the mass m2 moves upward with an acceleration of 2 ms–2. The value of F is
(Take g = 10 ms–2)
A
3360 N
B
3380 N
C
3120 N
D
3240 N
Answer
3120 N
Explanation
Solution
In frame of block of mass M moving with acceleration a.
m1a – T = 2m1
10a – T = 20 …(i)
T – m2g = 2m2
T – 200 = 40
T = 240 …(ii)
From equation 1 and 2
10a = 260
or, a = 26 m/s2
for block
F = (M + m2)a
F= 120 × 26
F= 3120 N
So, the correct option is (C): 3120 N