# Write equation of motion of lift when move up and when move down.

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Write equation of motion of lift when move up and when move down. +1 vote
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Let,

W = Weight carried by the lift

m = Mass carried by lift = W/g

a = Uniform acceleration

T = Tension in cable supporting the lift, also called Reaction of the lift

For UP MOTION

Net force in upward direction = T-W

Also Net Force = m.a i.e. T-W = m.a ...(i)

FOR DOWN MOTION Net force = W – T

Also Net Force = m.a

i.e. W – T = m.a ...(ii)

Note: In the above cases, we have taken weight or mass carried by the lift only. We have assumed that the weight carried by the lift includes weight of the lift also. But sometimes the example contains weight of the lift and weight carried by the lift separately. In such a case, the weight carried by the lift or weight of the operator etc, will exert a pressure on the floor of the lift. Whereas tension in the cable will be given by the algebraic sum of the weight of the lift and weight carried by the lift.