Q.

Two blocks of masses 40 kg and 30 kg are connected by a weightless string passing over a frictionless pulley as shown in the figure. The acceleration of the system would be

1 0.7 m s-2  
2 0.8 m s-2  
3 0.6 m s-2  
4 0.5 m s-2  

Ans.

(1)

Here, m1=40 kg

m2=30 kg,  θ=30°

Let T be the tension in the string and a be the acceleration of the system.

Their equations of motion are

m1gsin30°-T=m1a                ⋯(i)

T-m2gsin30°=m2a               ⋯(ii)

Adding (i) and (ii), we get

(m1+m2)a=(m1-m2)gsin30°

Substituting the given values, we get

(40+30)a=(40-30)×9.8×12=49

⇒  a=4970=0.7 m s-2