Two blocks of masses 10 kg and 20 kg are connected by a light spring as shown. A force of F = 200 N acts on the 20 kg mass as shown. At a certain instant, the acceleration of 10 kg mass is 12 m s⁻² towards right. At that instant the 20 kg mass has an acceleration of ____ m s⁻². (Surface is frictionless.)
Physics · Mixed Chapter
JEE Mains

Question

Two blocks of masses 10 kg and 20 kg are connected by a light spring as shown. A force of F = 200 N acts on the 20 kg mass as shown. At a certain instant, the acceleration of 10 kg mass is 12 m s⁻² towards right. At that instant the 20 kg mass has an acceleration of ____ m s⁻². (Surface is frictionless.)

Physics · Mixed Chapter

G1 Physics · Accepted Answer

Step 1: The 10 kg block is accelerated only by the spring on the frictionless surface. Spring force at the stated instant is Fₛ=m₁a₁=10×12=120 N to the right. Step 2: By Newton's third law, the spring exerts 120 N leftward on the 20 kg block. Net force there is 200−120=80 N. Step 3: a₂=80/20=4 m s⁻² to the right.