Answer: 2.3m/s
Explanation:
mass-energy balance: ke(f) + pe(f) = ke(o) + pe(o)
since we are looking for the point at the bottom of the pendulum, thats the reference point, the lowest in the system. pe(f) is 0, since h
ke(f)=0.5m x v(f)^2
pe(f)=0
ke(o)=0.5m x v(o)^2
pe(o)-mxgxh
find h by: drawing a triangle with the pendulum at the vertical, then displaced by 25 degrees , The difference in height is h, because cos(25)=(adj)/(hyp)=(2-h)/2. I found h=0.187m
In the m-e balance, cancel the masses in all the terms.
.5xv(f)^2 =0.5v(o)^2 +gxh
Given v(o) = 1.2 m/s and g = 9.8 then v(f) = 2.2595 m/s
Therefore V(0) = 2.3 m/s
