A small block of mass 4 kg is attached to a cord passing through a hole in a horizontal frictionless surface. The block is originally revolving in a circle of radius of 5 m about the hole, with a tangential velocity of 4 m/s. The cord is then pulled slowly from below, shortening the radius of the circle in which the block revolves. The breaking strength of the cord is 200 N
What will be the radius of the circle when the cord breaks?
a)
4.0 m
b)
1.0 m
c)
3.0 m
d)
2.0 m
What will be the radius of the circle when the cord breaks?
a)
4.0 m
b)
1.0 m
c)
3.0 m
d)
2.0 m
Question ID - 101295 | SaraNextGen Top Answer A small block of mass 4 kg is attached to a cord passing through a hole in a horizontal frictionless surface. The block is originally revolving in a circle of radius of 5 m about the hole, with a tangential velocity of 4 m/s. The cord is then pulled slowly from below, shortening the radius of the circle in which the block revolves. The breaking strength of the cord is 200 N
What will be the radius of the circle when the cord breaks?
a)
4.0 m
b)
1.0 m
c)
3.0 m
d)
2.0 m
A small block of mass 4 kg is attached to a cord passing through a hole in a horizontal frictionless surface. The block is originally revolving in a circle of radius of 5 m about the hole, with a tangential velocity of 4 m/s. The cord is then pulled slowly from below, shortening the radius of the circle in which the block revolves. The breaking strength of the cord is 200 N
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What will be the radius of the circle when the cord breaks? |
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a) |
4.0 m |
b) |
1.0 m |
c) |
3.0 m |
d) |
2.0 m |
(d)
The tension of the rope is the only net force on the block and it does not exert any torque about the axis of rotation. Hence, the angular momentum of the block about the axis should remain conserved
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constant
Let 
Let 
be the radius, velocity and tension when the string breaks
and
(i)
Note: The tension in the string is inversely proportional to the cube of the radius