Spring problems

When 2 body of mass m and 2m attached to a spring, the system is dropped from a hieght h such that the 2m mass is at the bottom .What do you say about the extension of the spring.

My sir said there will be no extension how? Please explain

• Try dropping a heavy object and a light object at the same time (without a spring between them), and see what happens. Apr 1, 2019 at 4:35
• @G.Smith it seems necessary to add 'with negligible air resistance on each object' as part of the condition. Apr 1, 2019 at 5:07

When to bodies free fall under the influence of gravity , their acceleration is same. If it provided that the bodies were moving with same speed or at rest when dropped, there should be no extension.

• Elimination of air resistance should be a condition for equal net acceleration. Apr 2, 2019 at 6:40

There has to be a force applied to spring for its expansion.

If the mass m is kept on the table and the mass 2m is attached to it using a spring, and if the 2m is hung while the m is still on table, the force applied by the gravity(i.e. 2mg) will pull the string and it will expand.

In contrast to the case when both the bodies are attached to the same string and body of mass 2m is hanging below of mass m but both the bodies are falling freely, there no weights attached to any of the body due to free fall, hence no pulling force on spring, no expansion.

a similar question

• fixed a typo in the third paragraph. Apr 2, 2019 at 6:12