Laws of MotionHard
Question
Two block of mass m1 and m2 are connected with a mass less spring and placed over a plank moving with an acceleration ′a′ as show in figure. The coefficient of friction between the blocks and platform is μ.


Options
A.spring will be stretched if a > μg
B.spring will be compressed if a ≤ μg
C.spring will neither be compressed nor be stretched for a ≤ μg
D.spring will be in its natural lenght under all conditions
Solution
Let a ≤ μg (i.e. friction is static)
Then both the blocks are rest w.r.t plank
Therefore spring will be in its natural length.
Now let a > μg (i.e. friction is kinetic)
Then both the blocks are moving with same acceleration w.r.t plank.
In this case spring force is equal to zero
Then both the blocks are rest w.r.t plank
Therefore spring will be in its natural length.
Now let a > μg (i.e. friction is kinetic)
Then both the blocks are moving with same acceleration w.r.t plank.
In this case spring force is equal to zero
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