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M3 Elastic springs-conservation of energy watch

1. I am a bit confused about when to use EE, PE, KE

when the ball hanging on a spring, hits the ceiling- EE is zero. how?

EE is calculated when there is a extenstion or compression, and in the above case the spring is compressed when the ball hits teh celing but in the exam paper mark scheme its taken to be zero.

so does that mean after its hits the celing and comes to REST, the ee is then only calculated ie is greater than zero. so in general when a object is at rest and the spring is streched or compressed EE can be calculated (i.e is greater than zero). pls help
2. when the ball hanging on a spring, hits the ceiling- EE is zero. how?
that depends on the position of the spring.
please post the question to know what you mean.

because if the spring was attached to the ceiling, and the ball is hanged vertically downward, then EE isnt zero when it reaches the ceiling, unless the spring is of natural length zero!!! which is not possible!

i too thought so it was imposible. i am very confused now. pls can u do the total intial energy = total kinetic energy equation for me.

A light elastic spring AB of natural length 0.8 m and moduls 5 N is attached at A to a ceiling which is 2.4 m abve the floor. A small ball of mass 0.2 kg is attached to the other end B and hangs in equilibrium

(i) calculate the length of the string (1.1136 m)
(ii) The ball is pulled down until it touches the floor with AB vertical and then its is released from rest. calculate the speed at which it hits the ceiling (5.74 m)

A second elastic string of modulus 5N and natural length L1 m where L1<2.4 is attached to the ball at B and to the floor vertically bellow A. The ball is held at rest on the floor with AB vertical an dthen its released

(iii) find the range of L1 for which teh ball will still hit the celing (1.162<=L1<=4.956)

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