To lift a load of 100 kg a distance of 1 m an effort of 25 kg must be applied over an inclined plane of length 4 m. what must be done to lift the load 2 m, using the same effort? a) use an inclined plane of length 8 m. b) use an inclined plane of length 2 m. c) use an inclined plane of length 10 m. d) use an inclined plane of length 16 m.

Using conservation of energy law:-
∑ work in = ∑ work out
and work= force* displacement 
so when we wanted to move a 100kg a distance of 1m 
we multiplied 100*1 = work out
so work in should be equal to 100*g Joules, where g is the acceleration due to gravity.
so workout = 100*g = 25*g *x (divide both sides by 25*g)
x=4m 

by the same way:-
------------------------
work in = 100kg * 2m * g (m/)= work out
so work out = 25*x*g = 200* g (divide both sides by 25*g)
x=8m

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