Question

In the system shown in figure all the surfaces are smooth. The 20kg block is prevented from rotating, i.e. comes straight down. Find its acceleration

(A) a = 5m/s² 

(B) a = 5.6m/s² 

(C) a = 6m/s² 

(D) a = 4m/s²

Answer 1

The correct option is (B) a = 5.6m/s² 

Explanation:

The acceleration (a) of all the 3 blocks will be same as the 20kg object defines it.

Tension in the string due to 5kg block = 5a
Tension in the string due to 10kg block = 10a
Force of gravity on 20 kg block = 20g

Equation of motion:

Force on 20 kg - (tension in string of 10 kg + tension in string of 5 kg) = actual downward force on 20 kg
20g - (10a + 5a) = 20a
196 - 15a = 20a
35a = 196
a = 5m/s²

Comments

Full solution plz

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(B) a=5.6m/s^2

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here is the complete solution