Answer:
Explanation:
Given
length of wire 
change in length 
mass of wire 
Young's modulus for silver 
load on wire 

change in length is given by

Where A=area of cross-section




also wire is the shape of cylinder so cross-section is given by





V^2=u^2 +2aS
U is found first by considering that first 8 secs and using v=u+at. {different v and u though}
V=-u+gt.
Magnitude of u = magnitude of v if there is no resistance ( because the conservation of energy says the k. E. must be the same when it passes you as when it left your hand).... up is negative here, down is positive.
V+v=gt
2v= g x 8
V=4xg.= the initial velocity for the next calculation
V^2=(4g)^2+(2xgx21)
So v can be calculated.
Explanation:
M.A = load / Effort
efficiency = M.A/V.R X 100
75 = M.A / 4 X 100
75 = 25 X M.A
M.A = 75/25 = 3
M.A = load / effort
3 = 100/E
E = 100/3 = 33.333