The figure shows a light spring balance connected to two blocks of mass 20 kg each. The graduations in the balance measure the tension in the spring. (a) What is the reading of the balance? (b) Will the reading change if the balance is heavy, say 2.0 kg? (c) What will happen if the spring is light but the blocks have unequal masses?

The figure shows a light spring balance connected to two blocks of mas

1.	The figure shows a light spring balance connected to two blocks of mass 20 kg each. The graduations in the balance measure the tension in the spring. (a) What is the reading of the balance? (b) Will the reading change if the balance is heavy, say 2.0 kg? (c) What will happen if the spring is light but the blocks have unequal masses?
Answer» (a) The reading in the balance is 20 kg. (b) Yes, if the balance is heavy the reading will change because the tension in the string will change. (c) When the blocks are of unequal masses, there will be net force on the system and it will start to move if the pulleys are friction-less. The tension in the string will change and so will be the reading of the balance.