A light spring has a 0.20 kg mass suspended from its lower end. A second mass of 0.10kg is suspended form the first by a thread. The arrangemet is allowed to come into static equilibrium. Determine the tensions in the spring and in the thread.
Then the thread is burnt through. Determine the immediate accelerations of the 2 masses when this happens.
In the 1st part where I took upwards to be +ve, the tension in the thread and spring were 0.981N and 2.94N respectively.
Then for the 2nd part
to find acceleration for thread,
summmation of forces = ma
0.981 (0.10)a
a = 9.81 ms-2
However I do not know if its in the upwards or downwards direction. Logically, the acceleration will be downwards but if I abide by the direction I allocated for part 1, acceleration will be UPWARDS since 'a' is a +ve value.
Similarly, I have a prob for getting the direction for the acceleration of the spring. Not the magnitude, but yes direction. I do think it's downwards acceleration. Or do I ignore the direction I have assigned earlier?
Thanks
Logically, initial direction of the first mass is upwards.
Because the initial tension in the spring is greater than the weight of the first mass 2.94N vs 2*9.81 N
It's like you pull the first mass downwards with the spring attached. Then you release the first mass.... The spring will accelerate the mass upwards.