Q.

A monkey of mass 40 kg climbs on a massless rope which can stand a maximum tension of 500 N. In which of the following cases will the rope break (Take g = 10 m s-2)

1 The monkey climbs up with an acceleration of 5 m s-2.  
2 The monkey climbs down with an acceleration of 5 m s-2.  
3 The monkey climbs up with a uniform speed of 5 m s-1.  
4 The monkey falls down the rope freely under gravity.  

Ans.

(1)

Here, mass of monkey, m=40 kg

Maximum tension the rope can stand, T=500 N

Tension in the rope will be equal to apparent weight of the monkey (R).

The rope will break when R exceeds T.

(1)   When the monkey climbs up with an acceleration a=5 m s-2

        R=m(g+a)=40(10+5)=600 N          ∴  R>T

        Hence, the rope will break.

(2)    When the monkey climbs down with an acceleration a=5 m s-2

         R=m(g-a)=40(10-5)=200 N          ∴  R<T

         Hence, the rope will not break.

(3)    When the monkey climbs up with a uniform speed v=5 m s-1, its acceleration a=0.

         ∴  R=mg=40×10=400 N             ∴    R<T

         Hence, the rope will not break.

(4)     When the monkey falls down the rope freely under gravity,

          a=g      ∴  R=m(g-a)=m(g-g)=0

          Hence, the rope will not break.