Answer: LED have the lowest cost of operation.
Explanation:
If we ignore the initial procurement cost of the items the operational cost of any device consuming electricity is given by

Among the three item's LED consumes the lowest power to give the same level of brightness as compared to the other 2 item's thus LED's shall have the lowest operational cost.
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Answer:
(a) the velocity ratio of the machine (V.R) = 1
(b) The mechanical advantage of the machine (M.A) = 0.833
(c) The efficiency of the machine (E) = 83.3 %
Explanation:
Given;
load lifted by the pulley, L = 400 N
effort applied in lifting the, E = 480 N
distance moved by the effort, d = 5 m
(a) the velocity ratio of the machine (V.R);
since the effort applied moved downwards through a distance of d, the load will also move upwards through an equal distance 'd'.
V.R = distance moved by effort / distance moved by the load
V.R = 5/5 = 1
(b) The mechanical advantage of the machine (M.A);
M.A = L/E
M.A = 400 / 480
M.A = 0.833
(c) The efficiency of the machine (E);

Answer with Explanation:
The capillary rise in 2 parallel plates immersed in a liquid is given by the formula

where
is the surface tension of the liquid
is the contact angle of the liquid
is density of liquid
'g' is acceleratioj due to gravity
'd' is seperation between thje plates
Part a) When the liquid is water:
For water and glass we have
Applying the values we get

Part b) When the liquid is mercury:
For mercury and glass we have
Applying the values we get

The negative sign indicates that there is depression in mercury in the tube.