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Stuck on mechanics problem regarding momentum/work

https://isaacphysics.org/questions/ballistic_pendulum?board=d84c1697-c41f-47eb-8ce3-4d0e3d723972

Using COLM, I've found that the combined mass (pendulum+bullet) has a common velocity of 1.2 ms^-1 . But I can't work out how to find how much it travels through the block (from which I can use trig to find the angle). I'm not sure if I can find the acceleration either from the data I have. Any ideas on what to do next?

Reply 1

username1560589

I believe that you can use this to calculate the kinetic energy, then equate this to gravitational potential energy gained at full swing. You can then use trig to find the angle

Reply 2

bobbricks

Original post by morgan8002

I believe that you can use this to calculate the kinetic energy, then equate this to gravitational potential energy gained at full swing. You can then use trig to find the angle

v=1.1952... ms^-1
I did 0.5(2.5+0.01)v^2 = (2.5+0.01)gh
so h=1.1952...^(2)/2g
so h=0.0728m

I did arccos(0.0728/3)=theta but that gives me the wrong angle.?

Reply 3

tiddlytom

I think the problem is in the conversion of the height of the block into an angle. Draw a diagram to work out the relation; you can see from your h that you expect a small angle.