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A lift a mass 1200 kg is raised from res...

A lift a mass `1200 kg` is raised from rest by a cable with a tension `1350 kg f` . After same time the tension drops to `1000 kg f` and the lift comes to rest at a height of `25 m` above its intial point `(1 kg - f = 9.8 N)`
What is the height at which the tension changes ?

A

`10.8 m`

B

`12.5 m`

C

`14.3 m`

D

`16 m`

Text Solution

Verified by Experts

The correct Answer is:
C
Acceleration `a_(1) = (1350 xx 9.8 - 1200 xx 9.8)/(1200)`
`= 1.225 m//s^(2)`
Retardation, `a_(2) = (1200g - 1000g)/(1200)`
`= 1.63 m//s^(2)`
`h_(1) + h_(2) = 25` …(i)
`nu = sqrt(2 a_(1) h_(1))` or `sqrt(2 a_(2) h_(2))`
or `2 a_(1) h_(1) = 2 a_(2) h_(2)`
`:. (h_(1))/ ( h_(2)) = (a_(2))/(a_(1))` ...(ii)
`= (1.63)/(1.225) = 1.33`
Solving these equations,we get
`h_(1) = 14.3 m`
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