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Mechanics question

Two particles A and B of mass 4kg and 3kg respectively are connected by a light in extensible string which passes over a smooth fixed pulley. The particles are released from rest with the string taut.

a) Find the tension in the string

b) When A has traveled a distance of 2m it strikes the ground and immediately comes to rest

Assuming that B does not hit the pulley find the greatest height that B reaches above its initial position.


So i found the tension to part a which is 33.6N

This is what i did for part b):

I found the a=1.4ms^2

For A: u=0 s=2 a=1.4 v=?
V^2=u^2 +2as
I got 2.4m/s 2sf

For B:
u=2.4 a=1.4 v=0 s=?
V^2=u^2 +2as
I got 2.1m

Can anyone help me identify where i faulted please.
Reply 1
Original post by Tynos


For B:
u=2.4 a=1.4 v=0 s=?
V^2=u^2 +2as
I got 2.1m

Can anyone help me identify where i faulted please.


That was a when there was tension pulling the particle upwards

That tension has gone so a has changed
Reply 2
Original post by TenOfThem
That was a when there was tension pulling the particle upwards

That tension has gone so a has changed


How could i find the changed acceleration?
Reply 3
Original post by Tynos
How could i find the changed acceleration?


You know what the acceleration is

If you drop a ball what is the acceleration
Reply 4
Original post by TenOfThem
You know what the acceleration is

If you drop a ball what is the acceleration



Ahh.. thank you.
Reply 5
Original post by TenOfThem
You know what the acceleration is

If you drop a ball what is the acceleration


I used 9.8ms^-2 but cannot seem to get 16/7, i get 0.3ms^-2
Reply 6
Original post by Tynos
I used 9.8ms^-2 but cannot seem to get 16/7, i get 0.3ms^-2


That is motion for part (b)

How far had it already moved
Reply 7
Original post by TenOfThem
That is motion for part (b)

How far had it already moved


Im confused.
Original post by Tynos
Im confused.


You're interested in the greatest height above its initial position.

This will equal the distance it moved when there was tension in the string, plus the distance it moved up when moving freely under gravity.

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