A. IMA: 4
The Ideal Mechanical Advantage (IMA) is given by:
where
is the input distance
is the output distance
For the pulley system in this problem, 
and 
, so the IMA is
B. MA: 3.59
The actual mechanical advantage (AMA), or simply the Mechanical Advantage (MA), is given by
where 
is the output force and 
is the input force. For the pulley system in this problem, 
and 
, so the MA is
C. Efficiency: 89.8 %
The efficiency of a machine is equal to the ratio between the MA and the AMA:
Therefore, in this case,
Answer:
Explanation:
Here image distance is fixed .
In the first case if v be image distance
1 / v - 1 / -25 = 1 / .05
1 / v = 1 / .05 - 1 / 25
= 20 - .04 = 19.96
v = .0501 m = 5.01 cm
In the second case
u = 4 ,
1 / v - 1 / - 4 = 1 / .05
1 / v = 20 - 1 / 4 = 19.75
v = .0506 = 5.06 cm
So lens must be moved forward by 5.06 - 5.01 = .05 cm ( away from film )
It’s 49% of its original gig hope this helps!
