Particles A and B, of masses 0.3 kg and 0.7 kg respectively, are attached to the ends of a light
inextensible string. The string passes over a ﬁxed smooth pulley. A is held at rest and B hangs freely,
with both straight parts of the string vertical and both particles at a height of 0.52 m above the ﬂoor
(see diagram). A is released and both particles start to move.
(i) Find the tension in the string. [4]
When both particles are moving with speed 1.6 m s−1
the string breaks.
(ii) Find the time taken, from the instant that the string breaks, for A to reach the ﬂoor.

Question

Particles A and B, of masses 0.3 kg and 0.7 kg respectively, are attached to the ends of a light
inextensible string. The string passes over a ﬁxed smooth pulley. A is held at rest and B hangs freely,
with both straight parts of the string vertical and both particles at a height of 0.52 m above the ﬂoor
(see diagram). A is released and both particles start to move.
(i) Find the tension in the string. [4]
When both particles are moving with speed 1.6 m s−1
the string breaks.
(ii) Find the time taken, from the instant that the string breaks, for A to reach the ﬂoor.

abmon98 · Answer

http://maxpapers.com/wp-content/uploads/2012/11/9709_w13_qp_4.pdf 6ii

anonymous · Answer

When the blocks are left free, tension remains the same at all time provided the string does not break.
Use Newton's laws to find the acceleration and in turn the tension. And the rest all is kinematics.