Motion of masses connected by a string over a pulley

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The discussion revolves around a physics problem involving two masses connected by a string over a pulley. Key points include calculating the speed of the particles before one mass hits the ground, determining the impulse exerted on the ground, and analyzing the subsequent motion of the masses. There is debate about the application of conservation of momentum when the string becomes taut, with differing opinions on whether to treat the interaction as elastic or inelastic. Ultimately, the complexity of the problem leads to discussions about the assumptions made regarding the nature of the string and the forces involved. The conversation emphasizes the need for clarity in interpreting the problem's conditions.
  • #31
ii) Impulse on ground when mass B impacts: 2mΔv ?
 
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  • #32
neilparker62 said:
ii) Impulse on ground when mass B impacts: 2mΔv ?

Yes, sorry. The mass should be 2m.For (v) :
Distance of B = twice the distance when it accelerates upwards + decelerate to stop (when A hits the ground)

Speed of B when A hits the ground
v^2 = (\frac{1}{3} \sqrt{\frac{2gh}{3}})^2 + 2 . \frac{g}{3} . 2h
v^2 = \frac{38gh}{27}

Distance traveled by B when decelerating:
v^2 = u^2 - 2gd
0 = \frac{38gh}{27} - 2gd
d = \frac{19h}{27}

So total distance
= 4h + 2 . \frac{19h}{27}
= \frac{146h}{27}

For (vi), I think I need to use formula of sum to infinity of geometric progression but I can not find the ratio. The distance traveled by B:
a. when released from rest until hits the ground = h
b. between first hit and second hit = \frac{146h}{27}
c. between second hit and third hit (repeating the same process as (v)) = \frac{1298h}{243}

How to find the total distance?

Thanks
 
Last edited:

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