Two blocks of respective masses m1 = 0.77 kg and m2 = 5.6 kg stand without motio
ID: 2238301 • Letter: T
Question
Two blocks of respective masses m1 = 0.77 kg and m2 = 5.6 kg stand without motion on a frictionless horizontal table. A spring is compressed between the two blocks, but theblocks remain motionless because they are tied to each other by a cord
The masses of the spring and the cord are negligible compared to the masses of the blocks. Once the system is set up, the cord is burned by a match and the blocks are pushed apart by the spring.
Once the spring is completely relaxed, it detaches from the m1 block, and the blocks continue to move away from each other at respective speeds v1 and v2.
Given m1 = 0.77 kg, m2 = 5.6 kg, v2 =3.3 m/s, but v1 is not given.
How much energy was stored in the compressed spring before the cord was burned?
Answer in units of J
Explanation / Answer
momentum is conserved and initial momentum was 0 : Final momentum = initial momentum = 0 -0.77*v1 + 5.6*3.3 = 0 v1 = 24 m/s Energy stored in the spring = kinetic energy of the blocks Energy stored in the spring = 0.5*0.77*24^2 + 0.5*5.6*3.3^2 = 252.252 J
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